Topic: Gerunds & Participles,

Best Answer Explained in Below-:

The correct choice in the sentence "--------- two months at sea, he came back healthier than ever." is option C: "Having spent." This gerundial phrase indicates that the subject (he) completed the action of spending two months at sea before the action of coming back occurred.

Let's break down the options:

A) "Spending" is a present participle that suggests an ongoing action, which does not fit well with the completed action implied in the rest of the sentence.

B) "Being spent" indicates a passive condition that doesn't accurately convey the subject actively engaging in the experience of two months at sea.

C) "Having spent" is in the perfect participle form, which effectively communicates that the two months at sea were completed before he returned. It emphasizes the result of that experience.

D) "Having been spent" also implies a passive experience and suggests he was expended or consumed by the two months at sea, aligning poorly with the idea of returning healthier.

Therefore, "Having spent" aptly illustrates the sequence of events and emphasizes the transformation that follows the completed action, making option C the best choice.