请问补充101题

The speculative fever of the Roaring Twenties infected rich and poor alike; vast quantities of people were dangerously overextended, credit was absurdly easy to obtain, and most brokerage houses required only ten percent cash for stocks bought on “margin.”(P2 F-2)

(A) rich and poor alike; vast quantities of people were dangerously overextended

(B) both rich and poor alike; large amounts of people dangerously overextended themselves

(C) rich and poor alike; great numbers of people were dangerously overextended

(D) both rich and poor alike; vast amounts of people dangerously overextended themselves（C）

       (E) both rich and poor; great quantities of people were dangerously overextended

分号后面的三句话用豆号分开，如何理解？

我觉得是并列结构。

句子1+句子2+and+句子3

原句句子结构合理只是quantity只能修是不可数名词。