GMAT Critical Reasoning (CR) | Re: Lark Manufacturing Company initiated a voluntary Quality Cir

What you said in bold implies that B weakens the argument
The conclusion is - Participation in a Quality Control Program causes less satisfaction with the job

One way to weaken a cause and effect conclusion is to find an alternate cause for the effect.

Now since people who didn't even participate in the QCP felt less satisfied with their job and people who did participate
...

---