单项选择题
A．offered to help without knowing what to do B．did not want to put themselves in any danger C．realized the trouble but could do nothing about it D．did not know there was something wrong with the ship
A．the tide was not suitable B．she had run aground on sand C．her engines had broken down D．most of her crew had gone ashore
A．monitor the hours of doctors by themselves B．make sure that the doctors who treat them have had enough sleep C．ask for legal control of the hours of doctors D．allow their doctors to sleep several hours before the operation