The use of adverbs in english

I just realized that I need to get help with understanding how to use adverbs in English. Let's say that a guy is nice, and he performs every action in that way.

Does he:
a) act nice
b) act nicely

Which one is the correct one and why is it so? Don't be afraid to use grammatical terms.

>>1
The former. Acting nicely means the manner of his acting is nice, which wouldn't make much sense unless you were referring to an actor's ability. You might play nicely or behave nicely.

>>7
Implying ebonics is simplified.