Exercise: active to passive. 01.- An old woman feeds the pigeons.
The pigeons by an old woman.
02.- A burglar broke the window.
The window by a burglar.
03.- Someone has made a mistake.
A mistake .
04.- Everyone is going to love her.
She by everyone.
05.- Cervantes wrote 'Don Quixote'.
'Don Quixote' by Cervantes.
06.- She is helping my sister.
My sister by her.
07.- Pamela will drive the bus.
The bus by Pamela.
08.- I was watering the plants.
The plants by me.

Exercise: active to passive.

01. The pigeons are fed by an old woman.
Explanation: The subject "An old woman" is replaced with "The pigeons" as the new subject in the passive voice. The verb "feeds" is changed to "are fed" in the passive voice. The preposition "by" is used to indicate the agent of the action, which in this case, is "an old woman".

02. The window was broken by a burglar.
Explanation: The subject "A burglar" is replaced with "The window" as the new subject in the passive voice. The verb "broke" is changed to "was broken" in the passive voice. The preposition "by" is used to indicate the agent of the action, which in this case, is "a burglar".

03. A mistake has been made.
Explanation: In this sentence, the subject remains the same in the passive voice. The verb "has made" is changed to "has been made" in the passive voice.

04. She is loved by everyone.
Explanation: The subject "Everyone" is replaced with "She" as the new subject in the passive voice. The verb "is going to love" is changed to "is loved" in the passive voice. The preposition "by" is used to indicate the agent of the action, which in this case, is "everyone".

05. "Don Quixote" was written by Cervantes.
Explanation: The subject "Cervantes" is replaced with "'Don Quixote'" as the new subject in the passive voice. The verb "wrote" is changed to "was written" in the passive voice. The preposition "by" is used to indicate the agent of the action, which in this case, is "Cervantes".

06. My sister is helped by her.
Explanation: The subject "She" is replaced with "My sister" as the new subject in the passive voice. The verb "is helping" is changed to "is helped" in the passive voice. The preposition "by" is used to indicate the agent of the action, which in this case, is "her".

07. The bus will be driven by Pamela.
Explanation: The subject "Pamela" is replaced with "The bus" as the new subject in the passive voice. The verb "will drive" is changed to "will be driven" in the passive voice. The preposition "by" is used to indicate the agent of the action, which in this case, is "Pamela".

08. The plants were watered by me.
Explanation: The subject "I" is replaced with "The plants" as the new subject in the passive voice. The verb "was watering" is changed to "were watered" in the passive voice. The preposition "by" is used to indicate the agent of the action, which in this case, is "me".

In passive voice sentences, the subject receives the action instead of performing the action. The agent (the one performing the action) is introduced using the preposition "by". It is important to note that not all active voice sentences can be converted to passive voice and vice versa, as it depends on the structure of the sentence and the meaning conveyed.