Answer: C. I was
surprised by how loud my new baby sister could cry I might have to get ear
plugs.
Explanation: A
run-on sentence is a sentence that conjoins thought with the usage of
conjunctions and punctuation such as a comma or semi-colon. Choice C did not
use any punctuation, besides a period (which doesn't matter in this case) and
did not contain any conjunctions whatsoever.
Choice A is
incorrect because the word "so" was used to bridge two thoughts.
"So" is a conjunction. Also, a comma was used, so we know this isn't
a run-on sentence.
Choice B is
incorrect because the word "and" was used merge two thoughts.
"And" is a conjunction.
Choice D is
incorrect because a semi-colon was used to couple two thoughts into one
sentence.
Thus, the answer is
Choice C.
