Answer:
B) Tell me whether or not you'll be able to make the party by Friday.
Explanation:
The imperative mood is a grammatical mood which expresses orders, prohibitions and requests. In this answer, it presents a question in the form of a sentence. The subject is asking for the party by Friday.
The answer must be know because of the subject who demand to know the answer. This is emphatically in part of the sentence "Tell me whether or not". The imperative mood is present in a direct request for an answer.
