We see a 3:2 split on the usage of Amount and Number. But since it refers to People, which are countable, the correct construct is Number.
This leaves us with C & D. Now this one is tough to differentiate between C & D.
Hopefully is an adverb and needs to a modify a verb. Otherwise "I hope" is more preferable.
Incorrect: Hopefully, we will win
Correct:" I hope we win
Also Correct: I prayed hopefully, we will win
So in this context, C is incorrect
The Correct answer is D.