Choose the correct form of adverb for the given sentence:
This bus goes ______ fast.

Incredibly: Surprisingly and in a very unlikely way.
Ex: incredibly, she survived the crash.
As per the sentence, The bus goes at some high speed which is quite surprising.
So, the best adverb to be used here is 'incredibly'.
Hence, option 2 is the best answer.
The correct sentence is: This bus goes incredibly fast.