Complete the sentence with the correct form of the verb in brackets: "Since the operation she has ____ (get) noticeably stronger."

Explication

After has the sentence needs a past participle, and this verb has two standard ones. British writing uses got — she has got stronger — while American English uses gotten for a change of state like this one, so has gotten stronger is equally correct and both spellings are accepted here. The base form would leave the perfect with no participle at all.