再问GWD3-32

Newspaper editorial:

In an attempt to reduce the crime rate, the governor is getting tough on criminals and making prison conditions harsher.  art of this effort has been to deny inmates the access they formerly had to college-level courses.  However, this action is clearly counter to the governor’s ultimate goal, since after being released form prison, inmates who had taken such courses committed far fewer crimes overall than other inmates.

Which of the following is an assumption on which the argument depends?

1. Not being able to take college-level courses while in prison is unlikely to deter anyone from a crime that he or she might otherwise have committed.
   
2. Former inmates are no more likely to commit crimes than are members of the general population.
   
3. The group of inmates who chose to take college-level courses were not already less likely than other inmates to commit crimes after being released.
   
4. Taking high school level courses in prison has less effect on an inmate’s subsequent behavior than taking college-level courses does.
   
5. The governor’s ultimate goal actually is to gain popularity by convincing people that something effective is being done about crime

答案是C。lawyer关于A的解释是说，取非以后，A选项变为措施（不让读大学课程）可能(likely)有效。

取非的方法对于假设型的题目是很有效的方法，但是，unlikely取非是likely吗？好像对于这种语句的取非和普通语句不太相同阿。