future tense and future continuous tense

Both answers are possible.

Hendy GunawanI know the answer is A, but, could I answer B ? I think the answer makes sense as well. If not, why ?

It makes sense in some future scenario:
You will be having something to drink at the party tonight, won't you? If so, I have to find someone else to be my designated driver.

But without that future context, ( a) is called for. The sc

Thanks for the explanation, all. So, the context is about an offer, not future action. That's why the answer A. But, in other context, we can use the tenses intercangably, can't we ?
For example : "I will think/will be thinking about your offer."
Even if we don't use the future context, we can still use 'future progressive' tense ? It's just sort of affirmation. What do you think ?

Hendy Gunawan "I will think/will be thinking about your offer."

These are interchangeable. The progressive indicates the duration of your thinking process, so has a somewhat more serious tone.

The progressive is most often used in circumstances of time duration, for instance when a friend is very sick:

I will be thinking about you.

Okay, it's clear now. Thank you for your kind reply, AlpheccaStars. You have helped alot in enlightening my mind about grammar.