Answer:
B. support
Step-by-step explanation:
Since there is no line provided, I'll explain the original meaning of the word and hopefully it will help.
The word comes from the Latin validare which means "to make something valid or legal".
Basically, its meaning is the act of checking and approving something. Also, it can mean providing a proof or an evidence to a certain claim or theory.
The closest meaning to this word from the given answers has the word "support". For example, if one wants to provide evidence to support his theory, we could say that he wants to validate it.