Question

Which verb agrees in number with its subject? The forests near my home __________ many different types of trees and plants. A. contain B. has contained C. contains D. is containing

Answer 1

Take out the bare parts: the subject and verb: forests _____.
If you still can't tell, assimilate it to something easier. Let's say "they are". 
Both "forests" and "they" are plural. 
Now, you wouldn't say "they is"; the verb also has to be plural. 
Back to "forests _____": forests contain. (A)
By the Process of Elimination, C and D are incorrect. You also cannot fill it out with "has contained" because that is singular. It would be "have contained", but that does not make sense in the context. 
So, the final answer would sound like this: 
The forests near my home contain many different types of trees and plants.

I hope that clarifies the problem (: