Concept:The correct answer depends on two rules: the base form after "will", and the standard idiom for taking an examination in British and West African English.
Explanation:The word "will" is a modal verb used to show future time.
After a modal verb, we must use the base form of the main verb, without "to".
Therefore, "will sit" is the correct grammatical structure.
The forms "sitting", "seat", and "set" do not fit after "will" in this meaning.
In British and West African English, the proper expression is "sit an examination", not "seat an examination" or "set an examination".
"Seat" refers to a place to sit, while "set" means to place something down, so they are both incorrect here.
Hence, the sentence should read: The students will sit the entrance examination next year.
Answer:A. sit