关于GMAT逻辑的题

关于GMAT逻辑的题
Industrial accidents are more common when some of the people in safety-sensitive jobs have drinking problems than when none do.Since,even after treatment,people who have had drinking problems are somewhat more likely than other people to have drinking problems in the future,any employer trying to reduce the risk of accidents should bar anyone who has ever been treated for a drinking problem from holding a safety-sensitive job.
Which of the following,if true,most seriously undermines the argument above?
A.Some companies place employees who are being treated for drinking problems in residential programs and allow them several weeks of paid sick leave.
B.Many accidents in the workplace are the result of errors by employees who do not hold safety-sensitive jobs.
C.Workers who would permanently lose their jobs if they sought treatment for a drinking problem try instead to conceal their problem and continue working for as long as possible.
D.People who hold safety-sensitive jobs are subject to stresses that can exacerbate any personal problems they may have,including drinking problems.
E.Some industrial accidents are caused by equipment failure rather than by em
C选项是如何起得削弱作用呢?