You should explain the reasons for a negative message except in job refusals and a. problems with customer orders b. credit denials c. refusals of routine workplace requests d. communication involving layoffs

A negative message should definitely be explained when dealing with any problem related to customer's orders as the satisfaction of the customer is a major effective factor in any business. 
Also refusals of routine workplace requests and communication involving layoffs require explanation of any negative message.

Based on this:
You should explain the reasons for a negative message except in job refusals and credit denials.
Choice: B