单项选择题

This passage is mainly about ______. ( )

A．the beginnings of oceanography
B．the laying of the first undersea cable
C．the investigation of ocean depths
D．the early intercontinental communications

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单项选择题

It was ______ that asked Maury for help in oceanographic studies. ( )

A．the American Navy
B．some early intercontinental travellers
C．those who earned a living from the sea
D．the company which proposed to lay an undersea cable

单项选择题

The aim of voyages Maury encouraged in the 1840s was ______. ( )

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