下列哪种情况不属于雷达航行参考图的功能（）.

A、有利于驾驶员识别航道

B、能准确地标示横驶区

C、便于准确判定船位

D、能提供选择正确航路的依据

Many of them turned a deaf ear to his advice, __________ they knew it to be valuable.

A．as if

B．now that

C．even though

D．so that