The correct answer among the choices is option D. The word "swiftly", which is italicized in the example, is an adverb. An adverb modifies a verb, an adjective or other adverbs. In the sentence, the verb modified is swim which is a verb.
Both C and D.
"will" in will be is a linking verb saying which tense it is in or indicating.
I think the answer is " Problem solving can be achieved through a systematic strategy that involves analyzing the problem."
