Answer: it's a because the answer c makes no sense and theirs no way for it to form from a volcano
The bond between one carbon atom and one oxygen atom is polar but due to the fact that there is another oxygen attached to the carbon which has the same electronegativity value as the oxygen on the other side, the effect of polarity is canceled.

is non-polar because the oxygens symmetrically alligned on the opposite sides of the carbon cancel the polarity effect.
You should always, and I mean always, use a <u>coverslip</u> on your slide. Without it, the contents on it would slip off and there'd be a big mess.
For extra security:
<em>Always make sure your stage clips are working! :)</em>
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I hope I helped! :)