In active verb sentences, the thing doing the action is the subject of the sentence and the thing receiving the action is the object. Most sentences are active.
eg. "
John washes the dishes" or "
The professor teaches the students"
Passive verb sentences are essentially the flip side of the above... so the thing receiving the action is the subject of the sentence and the thing doing the action is optionally included near the end of the sentence. Passive form is usually used if the thing receiving the action is more important or should be emphasized. Passive form is often used if you do not know who is doing the action or if you do not want to mention who is doing the action.
Eg. "
The dishes are washed by John" or "
The students are taught by the professor"
Consistant tense.... I think they just want you to write about 'whatever' in it's entirety from a future, past or present perspective.
Here is a page you may find useful on
subject-verb agreement
Hope this helps!
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