Image. Like, the way that cold red dripping popsicle forms an image in your head.
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 (:
The one that is the best way to find the correct answer for a sentence completion question on a reading test is : c. look at the main parts or the paragraph and infer the answer
The main parts is basically the core of the content. If you find it, it would be really likely that you could answer a question about it
hope this helps