蓄电池电解液不足时，可添加（）。

A.蒸馏水

B.水解液

C.矿泉水

D.稀硫酸

Which is NOT a distress signal?（）

A.A continuous sounding with any fog signal apparatus

B.A signal sent by radiotelephone consisting of the spoken word Mayday

C.An International Code Signal of N.C

D.The firing of green star rockets or shells