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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.”

(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）

请问：

great numbers 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.”在句中作什么成份？

对分号前面内容的解释；；；