In addition to the revised curriculum requested last semester, the students are now demanding that a new grading system be instituted.
(A) In addition to the revised curriculum requested last semester, the students are now demanding that a new grading system be instituted.
(B) In addition to the revised curriculum that had been requested last semester, the students are now demanding that a new grading system be instituted.
(C) The students are now demanding that a new grading system be instituted in addition to the revised curriculum they requested last semester.
(D) Added to the revised curriculum that was requested last semester by the students, they are now demanding the institution of a new grading system.
(E) Added to the new curriculum requested last semester, the students have now demanded the institution of a new grading system.
D and E are using Verbed modifiers incorrectly, since they and the students (Subjects of the main clause respectively) can not be added to the curriculum. Hence they are out
in B tense had been requested doesn't go with any past tense verb and is unnecessary. Hence out
Between A and C the difference is subtle but that of a meaning.
In C the students are demanding that (that clause includes in addition to the revised curriculum - something students requested earlier not that they are demanding now)
A clears it up clearly that In addition to the curriculum, students are now demanding. Hence Correct.