There is no doubt that “great numbers of students, of all ages, are overwhelmed by” the plethora of resources and searching tools in the changing electronic library, and they cannot function well unaided.
(A) great numbers of students, of all ages, are overwhelmed by
(B) vast quantities of students, of all ages, are overwhelmed by
(C) vast quantities of students at all ages are overwhelmed by
(D) a great number of students at all ages is overwhelmed by