求助一道逻辑题

david0106

Teenagers are often priced out of the labor market by the government-mandated minimum-wage level because employers cannot afford to pay that much for extra help. Therefore, if Congress institutes a subminimum wage, a new lower legal wage for teenagers, the teenage unemployment rate, which has been rising since 1960, will no longer increase.
Which of the following, if true, would most weaken the argument above?
(A) Since 1960 the teenage unemployment rate has risen when the minimum wage has risen.
(B) Since 1960 the teenage unemployment rate has risen even when the minimum wage remained constant.
(C) Employers often hire extra help during holiday and warm weather seasons.
(D) The teenage unemployment rate rose more quickly in the 1970’s than it did in the 1960’s.
(E) The teenage unemployment rate has occasionally declined in the years since 1960.

这道题目是说wage降低后，雇佣者就会雇佣更多人 所有unemployment rate就会降低。求削弱。
但是该题的答案说的是 最低wage不变的话 unemployment rate还是会升高。这个和题目中假设的条件不一样，怎么会削弱啊？

sdcar2010

Premise : The minimum wage is so high that it prevents employers to hire teenager.

Conlusion : If the minimum wage is lowered for teenagers, their unemployment rate will no longer increase.

The assumption is that the minimum wage is responsible for the rising unemployment rate in teenagers.

B casts doubt on the assumption since when the minimum wage remained constant, the teenage unemployement rate was still rising.  Clearly, something else caused the teenage unemployment other than or in addition to minimum wage. Thus, B make the conclusion unlikely.