单项选择题
A．to make some sound experiments in the oceans B．to collect samples of sea plants animals C．to estimate the length of cable that was to be made D．to measure the depths of two oceans
A．the beginnings of oceanography B．the laying of the first undersea cable C．the investigation of ocean depths D．the early intercontinental communications
A．doubted B．gave proof to C．challenged D．agreed to