期货公司的下列（）无效。

A．私下对冲行为

B．透支交易行为

C．超量平仓行为

D．与客户对赌行为

What following is not among the function of SOLAS ships?（）

A.receive shore-to-ship distress alerting

B.transmit ship-to-shore distress alerting

C.receive message for public correspondence

D.transmit and receive locating signals