My ans is C.
a) The second survey occured during a period of recession when rumors of cutbacks and layoffs at Lark Manufacturing were plentiful. => presents other cause, so A weakens the argument
B) The survyes also showed that those LArk machine operators who neither participated in Quality Circles nor knew anyone who did so reported the same degree of lessened satisfaction with their work situations as did the Lark machine operators who participated in Quality Circles. =>not only did workers who participated in the program complain, but workers who didn't participate also complain. So, the program itself does not cause job dissatisfaction. It must be sth else. This weakens the argument.
C) While participating in Quality Circles at Lark Manufactoring, machine operators exhibited two of the primary indicators of imprioved job satisfaction:increased productivity and decresed absenteeism. => does not weaken the argument
D) Several workers at LArk Manufactoring who had participated in Quality Circles while employed at otehr companies reported that while participating in Quality Cirlces in their previous companies, their work satisfaction had increased. => their expectation is higher. It weakens the argument
E) The machine operators who participated in Quality Circles reported that when the program started, they felt that participation might improve their work situation. =>same as D, the workers had high expectation at the beginning. Weakens