Part of the proposed increase in state education spending is due to higher enrollment, since the number of students in public schools have grown steadily since the mid-1980's and, at nearly 47 million, are at a record high.
(A) enrollment, since the number of students in public schools have grown steadily since the mid-1980's and, at nearly 47 million, are at
(B) enrollment, with a number of students in public schools growing steadily since the mid-1980's and, at nearly 47 million, reaching
(C) enrollment: since students in public schools have grown steadily in number since the mid-1980's and, at nearly 47 million, have reached
(D) enrollment: the number of students in public schools has grown steadily since the mid-1980's and, at nearly 47 million, has reached
(E) enrollment: students in public schools have grown steadily in number since the mid-1980's and, at nearly 47 million, are at
原文大致意思：教育收费上涨主要是因为入学人数多了，并且到达了最高点
题目分析：原文说到学生数量的时候提到了一个并列关系，就是have grown steadily和 are at a record high这两个之间形成的并列关系。
A用have和are而发起者是number，主谓不一致，干掉。
B选项说reaching就和前面形成不了并列关系了，干掉。
C reach的发起者变成students了，不对，学生是无法到达历史最高点的。
D用has grown和has reached，形成了并列关系，并且主谓保持一致，留着。
E are at a record high的发起者变成学生了，犯的错误和C类似，杀！
