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.
I would say a, because the colon is being used to explain the statement that comes before it
He broke his arm riding his bike down the mountain.
She suddenly pressed the break when the car cut in front of her.
(I'm not sure if you meant two different sentences or one, if so just tell me and I can come up with something :) )
Answer:
his little tool boxes as well—they were treasures
Explanation: