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

Each of the following, if true, casts doubt on the consulting firm's conclusion EXCEPT:

A In the investigation of working conditions, no account was taken of the fact that for the past year many Company P employees 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 firm's conception of what constitutes 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

OA: D

I am confused between B and D.
I chose B because how workers in other companies are doing should have little to do with workers in company P because there is no relation shown in the argument. Can someone please help.