When a writer does not know who performed the action in a sentence, the writer can still write a grammatically correct sentence by

using the active voice.
using the passive voice.
ending the sentence with an infinitive.
ending the sentence with a preposition.

Using the passive voice

Explanation:

Ex:

Rice is grown in China.  (You don't know who grew the rice.)

Based on the information given, the passive voice can be used by the person.

A passive voice simply means the form of verb where the subject undergoes the action of the verb.

In a situation where the writer does not know who performed the action in a sentence, then the writer can still write a grammatically correct sentence by using the passive voice.

Learn more about passive voice on:

link

depends on your school

when i was in high school i took ap biology my senior year and it was the hardest one for me because my teacher finished the material within the first month of school and then went on to doing advanced college level it was horrible. but at a nearby school ap biology was one of the easier aps. also, it depends on what you are interested i like math a lot so ap calculus was easier for me than most but i hate history so ap us government was harder for me than most.