Continuous tense.
1) john often (to send) e-mail letters to his friends abroad.
2) paul (to write) an e-mail letter to his friend in canada
now. 3) margaret (to look) for a better job at the moment.
4) (to attend) language courses three times a week. 5) the
secretary (to be) busy now. she (to prepare) the documents
for the conference. 6) my elder brother (always to make fun)
of me! 7) the professor (not to eramine) patients now. he
(to give) a lecture to the students at the moment. he usually
(to examine) the patients in the morning. 8) the article
(to contain) the results of important researches in medicine.
9) you never (to tell) me about your problems at school. i'm
a bit surprised that you (to ask) me for a piece of advice now.
10) most oils .. (to boil) at 200-300 c. 11) the
(to have) lunch now? - no, they . they (to rehearse) in
the assembly hall. they (to perform) some new songs at the
concert tomorrow. doctors (to use) antibiotic drugs to
fight viruses? - no, antibiotic drugs (not to work) against
viruses. doctors usually (to prescribe) antibiotics against
bacterial infections. 13) max. (always to play) pranks on his
classmates! you (to wait) for a ferry? - yes, we
the ferry (to arrive) at four o'clock. 15) peter and tim
(to go) fishing next thursday? - yes, they often (to go)
fishing together. and they always (to invite) me to join them.​

1) sends
2) is writing
3) is looking
4) attend
5) is, is preparing
6) always makes fun
7) isn’t examining, is giving, examines
8) contains
9) tell, ask
10) boil
11) Are, having, aren’t, rehearse, will perform
12) Do, use, isn’t working, prescribe
13) always plays
14) Do, wait, do, will arrive
15) Will, go, they will, go, invite

1) John often ... (sends) e-mail letters to his friends abroad.

2) Paul ... (is writing) an e-mail letter to his friend in Canada now.

3) Margaret ... (is looking) for a better job at the moment.

4) We... (attend) language courses three times a week.

5) The secretary ... (is) busy now. She ... (is preparing) the documents for the conference.

6) My elder brother ... (is always making fun) of me!

7) The professor ... (is not examining) patients now. He ... (is giving) a lecture to the students at the moment. He usually ... (examines) the patients in the morning.

8) The article ... (contains) the results of important researches in medicine.

9) You never ... (tell) me about your problems at school. I'm a bit surprised that you ... (are asking) me for a piece of advice now.

10) Most oils .. (boil) at 200-300 C.

11) Are the musicians... (having) lunch now? - No, they aren't. They ... (are rehearsing) in the assembly hall. They ... (are performing) some new songs at the concert tomorrow.

12) Do doctors ... (use) antibiotic drugs to fight viruses? - No, antibiotic drugs ... (do not work) against viruses. Doctors usually ... (prescribe) antibiotics against bacterial infections.

13) Max (is always playing) pranks on his classmates!

14) Are you ... (waiting) for a ferry? - Yes, we are. The ferry ... (arrives) at four o'clock.

15) Are Peter and Tim ... (going) fishing next Thursday? - Yes, they are. They often ... (go) fishing together. And they always ... (invite) me to join them.​