Each of the scientists involved in the groundbreaking research, along with their lead supervisor, are confident that the findings will revolutionize medical treatment.

The correct answer to the question "Each of the scientists involved in the groundbreaking research, along with their lead supervisor, are confident that the findings will revolutionize medical treatment." is Option B: along with their lead supervisor, is confident.

The other options — A) along with their lead supervisor, are confident, C) and their lead supervisor, are confident, D) as well as their lead supervisor, have confidence — are incorrect for this GMAT Exam Prep question. As explained above: The subject of the sentence is 'Each,' which is singular. Phrases like 'along with' or 'as well as' are prepositional and do not change the number of the subject. Therefore, the singular verb 'is' is…