Revising involves a. checking for spelling errors b. checking for punctuation errors c. checking for content clarity and coherency d. checking the page limit

I've always been taught that revising involves checking for spelling, punctuation, and grammar.  Basically any kind of improvements.  Is this one of those questions where you check all that apply?    Revising also includes making sure you have stayed on topic and gives you the chance to remove things that may not really apply or add other things that may have been left out.  It's where the writer truly polishes everything up.
I hope this helps.