请教费费宝典中的一道题

When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast, of every 100 people who have used cocaine 99 will test positive. Thus, when a randomly chosen group of people is tested for cocaine use, the vast people is tested for cocaine use, the vast majority of those who test positive will be people who have used cocaine.

A reasoning error in the argument is that the argument

A.        attempts to infer a value judgment from purely factual premises

B.        attributes to every member of the population the properties of the average member of the population

C.        fails to take into account what proportion of the population have used cocaine

D.       ignores the fact that some cocaine users do not test positive

E.        advocates testing people for cocaine use when there is no reason to suspect that they have used cocaine

请问题目中最后一句话是什么意思啊？如何理解the vast...,the vast...这个结构？

谢谢！！

the last senctence is the same as the following:

Thus, if a randomly chosen group of people is tested for cocaine use, and if the vast people is tested for cocaine use, the vast majority of those who test positive will be people who have used cocaine.