The pilot lost control with the military base,       the plane crashed in the desert.

A．by means of which

B．for which

C．in case of which

D．as a result of which

（）是指债权人按照合同约定占有债权人的动产，债务人不履行债务时，债权人有权依法保留处置该财产，从将该财产折价或者拍卖.变卖的价款中优先赔偿。

A.保证

B.抵押

C.质押

D.留置