Out of your 3 possible answers, B. ones' is the correct one and I will explain why. Answer A is a contraction of one and is. When you put "one is" into the blank space you can tell that it is not right. Answer C is incorrect because when you place an apostrophe after an s it is implied that there should be another s that follows and so you do not need to put it there. This means that answer B is correct since it doesn't have the extra s.
"B. By the light of the moon, I tripped over a <span>rock" would be the only sentence with a dangling modifier, since in this case it is unclear what exactly is being modified, since the moon light and the tripping incident could be two, separate events in time. </span>
