All you can say about it is that it then vibrates perpendicular to the x-axis. But that could be up and down parallel to the y-axis, in and out parallel to the z-axis, or some of it in every possible direction perpendicular to the x-axis. We "polarize" the light when we want to pick out only one perpendicular direction and stop all the others.
I am not sure but i think the answer is C
I don't know if you need to complete this question or do it otherwise, however, I managed to find on the Internet on several places this completion of your sentence:
<span>Electric current flows through a long rod generating thermal energy at a uniform volumetric rate of q = 2 x 10</span>⁶ W/m³.
I'm not sure whether that is the answer you were looking for, but that's what I found.
