This question test our knowledge on comparison. Specifically on usage of As vs. Like. Fundamentally, we use 'like' to compare nouns and we use 'as' to compare clauses.
In a given case, we need a comparison between nouns - Mary vs. other students. Consequently, Option C is the best option.Mary, just as did the other students, objected to the squash casserole.
A. Mary, just as did the other students, objected to --> Though this option sounds correct I find it wrong. I prefer noun vs. noun comparison in a given case. Hence, I am not opting for this option.
B. Like the other students, Mary was objectionable to --> Changes the meaning. Mary was not objectionable per original sentence. This option means Mary was objectionable and so are the other students.
C. Mary, like the other students, objected to -->
CorrectD.
Mary objected, in the manner of the other students, to --> 'in the same manner
of the other students' is absolutely wrong. For comparison, we need 'as or like'. Usage of 'of' is just wrong.
E.
Mary, as the other students, objected --> use of 'as' to compare 'nouns' is grammatically wrong. Hence, this option is incorrect.