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. :)

the answer is; comparing the frequency of collisions with and without the device

this makes the anti-collision system an independent variable and the collisions a dependent variable. if there are fewer collisions with an anti-collision system that without, then it can be stated that the system is a success. essentially, collisions under an anti-collision system are compared with the frequency of collisions by cars with the human drivers.

i believe the answer is a or 1