not able to see the picture, can u plz type it

A,D and E can be easily eliminated

B)
I think the problem with B is the usage of the word "MOST"
Lets's negate the statement
A Diamond Dry-Cleaning Clerk's most time consuming task is to not performing customer credit checks

It is possible that performing credit checks is not the MOST important task.But still it may be one of the tasks that take more time.
Hence it is not essential.

C)
The director is assuming that the nature of both the businesses is exactly the same.
What if in Drycleaning business, customers are not willing to pay before their clothes are dry cleaned.
Rapid payment process won't be effective for this business.
and hence the decision taken by the director doesn't hold any water.

Hence C

Please post OA along with the source

Paraphrasing the argument:

Evidence: the convenience store is successful because it has fast check out

Conclusion: the dry cleaner will be successful if it has fast check out.

Assumption: what works for convenience stores will work for dry cleaners - in other words, the csutomers are looking for the same thing.

The time to make credit checks in not hte issue - customer needs is the issue.