I would think D because it answers why it was a good decision to buy Alaska from Russia.
Answer:
A adverb usually follows the verb, It can also precede the verb. Also a prepositional phrase functions as an adjective or adverb, and a prepositional phrase functions as an adjective or adverb. Also letting someone know you like them a lot just adds the adverb onto the verb. And being is an adverb and so it will always modify a verb in lieu of a noun.
Explanation:
