Customers are asked to make sure that they

Customers are asked to make sure that they

　Customers are asked to make sure that they ____the right change before leaving the shop.
 
　　A.will give
 
　　B.have been given
 
　　C.have given
 
　　D.will be given
 
　　答案：B
 
　　解析：考查宾语从句中时态兼语态。“找零”动作发生在“离开”之前，故用完成时。现在完成时表示某个动作或过程在过去某个时间已经开始，现在已经完成或可能继续延续下去。