请牛牛们进来看一看,我不理解kaplan test 1, 19

A confidential survey revealed that 75 percent of the employees of company P are dissatisfied with their jobs. How ever, an investigation into working conditions at the company showed nothing uncommonly bad. Therefore, company P's consulting firm conclouded that the employees' dissatisfaction must result from an unusually high incidence of psychological problems on their part.

Which of the followng, if true, strenthens the consulting firm's conclusion?
a In the investigation of working conditions, no account was taken of the fact that for the past year many Company P emplyees worked on a joint venture with Company O, at company O's facilities.
b Workers in many companies are dissatisfied although there are no apparent problems with their working conditions.
c the consulting firms conception of what contitutes uncommonly bad working conditions is not identical to that of Company P's employees.
d The reasons given by Company P's employees for their dissatisfaction varied greatly from employee to employee.
e A battery of tests performed on Acme's employees one month ago revealed no significant psychological stresses or problems.

这道题我有答案，但是我认为解释的很荒谬，所以想听听大家的解释，看看是不是确实我没有理解到位。答案是d。只解释为什么选d就可以了，其他选项我能够排除。谢谢

If the reasons varied greatly, it supports "an unusually high incidence".

Unusual means special, so different people have different reasons.

Feel free to correct me... 

Trying to throw in my two cents here...

The argument to strengthen here is the employees' dissatisfactions are caused by their own psychological problems which have nothing to do with any wrong-doings on the company's part.

That being said, D says everyone who complained gave very different reasons.  That means there is no COMMON reason that everyone shares.  If it was something done wrong by the company, then everyone would have at least some common reason against that.  But the fact is there is none, which suggests that everyone might have their own psychological problems.  It is "unusual" to have that many employees in one company that have psychological problem but the research suggests that it might be the case.

To make some fun out of it, most employees in this company are CRAZY!!!!!

Totally agree.