14. a) use the correct form of the verb in brackets in the passive voice. b) rewrite sentences 4, 7, 8, 9 and 12 in the active voice. 1. at present, research in physiology (to concentrate) on the integra- tion of the different activities of cells, tissues, and organs at the level of the intact organism. 2. some problems of mammalian physiology already (to investigate) from a classical-organ and organ-system point of view, but comparative studies in physiology (to continue) in future.
3. high milk yields (to maintain) if feeding rations (to calculate) on the basis of physiological parameters of animals. 4. in the 19th century, methods of the physical sciences (to apply) to physiology by carl ludwig, a famous german physiologist. 5. the project for scientific cooperation between the research institutes (to consider) at the conference next week. 6. in an early scientific classification, tissues (to divide) on the basis of the organ system of which they formed a part, for instance, nervous tissues. 7. the principles of experimentation in the life sciences (to suggest) by a french physiologist claude bernard in pothe 19th century.8. careful and rather expensive research (to carry out) by the biochemists at the cell level now. 9. the basis for the physiology of microorganisms (to provide) by the concept of comparative biochemistry. 10. common or general features usually (to find) at the cellular and molecular levels of organisation for animals and plants. 11. even now physiology is still of great importance among the functional sciences that (to relate) closely to the field of medicine. 12. the first journal which o devote) mainly to the publication of research results in physiology o publish) by sir michael foster, a professor of practical physiology at university college in london, in 1878.​

14. a) use the correct form of the verb in brackets in the passive voice.
1. At present, research in physiology is being concentrated on the integration of the different activities of cells, tissues, and organs at the level of the intact organism.

Explanation: In this sentence, the verb "to concentrate" is in the present continuous passive voice because the action of concentrating is happening right now and it is being done by someone (the researchers). Therefore, "is being concentrated" is the correct form of the verb in the passive voice.

2. Some problems of mammalian physiology have already been investigated from a classical-organ and organ-system point of view, but comparative studies in physiology will be continued in the future.

Explanation: In this sentence, the verb "to investigate" is in the present perfect passive voice because the action of investigating has already been completed in the past and it has been done by someone (the researchers). Therefore, "have already been investigated" is the correct form of the verb in the passive voice. The verb "to continue" is in the future simple passive voice because the action of continuing will happen in the future and it will be done by someone (the researchers). Therefore, "will be continued" is the correct form of the verb in the passive voice.

3. High milk yields are maintained if feeding rations are calculated on the basis of physiological parameters of animals.

Explanation: In this sentence, the verb "to maintain" is in the present simple passive voice because the action of maintaining happens regularly and it is done by someone (the farmers or the people responsible for feeding the animals). Therefore, "are maintained" is the correct form of the verb in the passive voice. The verb "to calculate" is in the present simple passive voice because the action of calculating happens regularly and it is done by someone (the farmers or the people responsible for feeding the animals). Therefore, "are calculated" is the correct form of the verb in the passive voice.

4. Carl Ludwig, a famous German physiologist, applied methods of the physical sciences to physiology in the 19th century.

(Active voice: In the 19th century, Carl Ludwig, a famous German physiologist, applied methods of the physical sciences to physiology.)

Explanation: In this sentence, the verb "to apply" is in the past simple active voice because the action of applying happened in the past and it was done by Carl Ludwig. Therefore, "applied" is the correct form of the verb in the active voice.

5. They will consider the project for scientific cooperation between the research institutes at the conference next week.

(Active voice: The project for scientific cooperation between the research institutes will be considered at the conference next week.)

Explanation: In this sentence, the verb "to consider" is in the future simple active voice because the action of considering will happen in the future and it will be done by the people responsible for considering the project. Therefore, "will consider" is the correct form of the verb in the active voice.

6. In an early scientific classification, they divided tissues on the basis of the organ system of which they formed a part, for instance, nervous tissues.

(Active voice: In an early scientific classification, they divided tissues on the basis of the organ system of which they formed a part, for instance, nervous tissues.)

Explanation: In this sentence, the verb "to divide" is already in the active voice and there is no need to change it to the passive voice because the sentence is already in the correct form.

7. A French physiologist, Claude Bernard, suggested the principles of experimentation in the life sciences in the 19th century.

(Active voice: Claude Bernard, a French physiologist, suggested the principles of experimentation in the life sciences in the 19th century.)

Explanation: In this sentence, the verb "to suggest" is in the past simple active voice because the action of suggesting happened in the past and it was done by Claude Bernard. Therefore, "suggested" is the correct form of the verb in the active voice.

8. The biochemists are carrying out careful and rather expensive research at the cell level now.

(Active voice: The biochemists are carrying out careful and rather expensive research at the cell level now.)

Explanation: In this sentence, the verb "to carry out" is already in the active voice and there is no need to change it to the passive voice because the sentence is already in the correct form.

9. The concept of comparative biochemistry provides the basis for the physiology of microorganisms.

(Active voice: The concept of comparative biochemistry provides the basis for the physiology of microorganisms.)

Explanation: In this sentence, the verb "to provide" is already in the active voice and there is no need to change it to the passive voice because the sentence is already in the correct form.

10. Common or general features are usually found at the cellular and molecular levels of organization for animals and plants.

Explanation: In this sentence, the verb "to find" is in the present simple passive voice because the action of finding happens regularly and it is done by someone (the researchers or scientists). Therefore, "are usually found" is the correct form of the verb in the passive voice.

11. Even now, physiology is still of great importance among the functional sciences that are closely related to the field of medicine.

Explanation: In this sentence, the verb "to relate" is in the present simple passive voice because the action of relating happens regularly and it is done by someone (the researchers or scientists). Therefore, "are closely related" is the correct form of the verb in the passive voice.

12. Sir Michael Foster, a professor of practical physiology at University College in London, published the first journal which was mainly devoted to the publication of research results in physiology in 1878.

(Active voice: In 1878, Sir Michael Foster, a professor of practical physiology at University College in London, published the first journal which was mainly devoted to the publication of research results in physiology.)

Explanation: In this sentence, the verb "to publish" is in the past simple active voice because the action of publishing happened in the past and it was done by Sir Michael Foster. Therefore, "published" is the correct form of the verb in the active voice.