As many is right. In D and E, D compared a number to the enrollment. This isn't right. So E
A) comparison incorrect. 80 million ppl to enrollmet
B) compariosn incorrect. "Those" stands in for "those people enrolled..." This means that we're comparing a number of people (80 million people) to simply" people.
C) Same problem as B
D) Again, we're comparing a number of people to "enrollment." Changing the comparison marker to "as many as" doesn't fix this.