You use a dash in place of a comma to add more of a sense of separation of thought, when inserting a phrase in the middle of a sentence. They signify a pause in your thought process, an interruption to include a relevant but somewhat non-continuous fact like this:

The greatest threat to the earth – most people would call it global warming – is not immediate enough to unite humanity.

Definitely not in place of exclamation point, I think your best answer listed is “D,” since a semicolon is also used to separate thoughts, and is similarly stronger than a comma.

Hope I helped you out.

Or a slash like this…– ?

At any rate, I think a “slash” would be used most effectively in place of a semicolon, in SOME instances. “I’m going to make a list of good clothes for him/her to wear to the prom.”

Hmmm.

It’s definitely not A., nor B., so we have a choice between C. and D. I just gave a (poor) example of D.

An example of C. might be: “I must get his/her clothes from the dry cleaner’s!”

No, I don’t like C.! It must be D. A better way to use it would be the — slash for D. “I have my homework here–where is your notebook?” Do NOT use the / slash after all!

But please, make up your own sentence to use as an example if you must!

Thanks, and good luck.