He waited until it was dark ____ nobody could see him clearly.

A．so that

B．in order to

C．although

D．However

下列有关富余水深的计算哪项是正确的？（）

A.富余水深=海图水深+当时当地的基准潮高-船舶静止时的最大吃水

B.富余水深=海图水深-当时当地的基准潮高+船舶静止时的最大吃水

C.富余水深=海图水深+当时当地的基准潮高-船舶静止时的平均吃水

D.富余水深=海图水深+当时当地的基准潮高-船舶航行时的最大吃水