Which of these is an agent of wedging

I would answer your question but i think you wanted to add options. next time you can just screen shot and actually i think you still can by pressing the edit button. And there are several types of wedges you could be talking about mechanical, frost, salt, etc.

You need to be a bit more specific. but i would be more than happy to answer your question. :)

it is either c or d and i know for sure it is not a or b