B. One of your troop members began to cry.
It doesn't explain why he is crying, and is the most suspenseful, but one could argue it was C, because they could have going the wrong direction, but B is the most suspenseful due to the crying and emotion in it.
Hope this helps, even though I just debated aloud.
Answer:
B. Have the United States Marine Corps been a part of the United States Armed Forces since 1775?
Answer: An Elliptical sentence ends with a pronoun im pretty sure.