The dance squad had eight members when it won the competition.
A relative clause can be used as an adjective or an adverb. Relative clauses must contain both a subject and a verb. They also begin with a relative pronoun (question words and that). The relative clause in the last option is "when it won the competition". It starts with "when" which is a relative pronoun. It describes when the action takes place which makes the entire clause an adverb. It has a subject "it" and a verb "won". Options B and C should be immediately thrown out because they do not have a relative pronoun. Option A does not work because there is no subject after "that".
MORE CAUTIOUS SORRY FOR PUTTING IT IN ALL CAPS BUT
If you look deep into the question, the answer would be telling someone something bad gently but if you were to look light into the question, the answer would just be rain comming down gently