Since the majority of customers are not complaining

Since the majority of customers are not complaining when they are dissatisfied, even those organizations most concerned with customer service have only a single opportunity to establish brand loyalty.

A. Since the majority of customers are not complaining
B. Since the majority of customers have not complained
C. Since the majority of customers do not complain
D. When the majority of customers do not complain
E. In the event that the majority of customers are not complaining

Can somebody please
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