单项选择题
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
A.or B.and C.but D.with
A. A lot of patients need a second operation. B. Doctors are not well trained to ensure successful operations. C. Demands for hip replacement exceed the number of surgeons. D. Replacement operation is becoming too expensive in U. S. hospitals.