GMAT Sentence Correction (SC) | Re: Since the movie was released seventeen UFOs have been sighted in the

I try to explain with what I got. This is a case of Active voice vs passive. Here 'they' represents UFO's only but that clause should be in passive voice which is not present in choice B. Because UFOs have to be sighted by someone and it is the not the case that UFOs have sighted in the past ten years.

Giving me + 1 kudos if my post is valuable with you

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