单项选择题
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．Suez Canal B．trans-Siberian Railroad C．Taj Mahal D．pyramids of Egypt
A．About half of Panama lies east of Miami. B．Panama is squeezed into the narrowest portion of Central America. C．Panama offers the lowest point in the North American continental divide. D．All of the above are tru