按现行海关规定，下列哪些货物要允许存人保税仓库：

A．由境内有经营权的外贸企业购买进口的进料加工业务备用料件

B．供应国际航行船舶的燃料和零配件

C．以寄售方式进口，用于进口机电产品维修业务的维修零配件

D．转口港澳的烟酒

After the class was _____, some of the students were asked to remain.[ ]

A. at an end      

B. in the end      

C. by the end      

D. at the end