For someone with an action must be performed in order to alleviate anxiety associated with a recurring thought

My  For someone with obsessive compulsive disorder, an action must be performed in order to alleviate anxiety associated with a recurring thought. 

Hope I helped! :D

Ithink the answer you are looking for is (b).

It is meant that like tapestry scientific theories often need to pull out since they are not relevant and often times the whole chain of theories may be pulled out.