9.
Your Answer is
Correct Answer is C
Explanation
Crouching behind shelters and trying to eliminate... is the result adverbial of the sentence, so it is separated from the front main clause by a comma, and C is correct.
Item A/B: Both are attributive clauses, modify field, and have semantic errors.
Item D: crouching... There is no comma in front of it, so the field is modified, and the semantics are wrong.