单项选择题
A．and B．but C．yet D．so
A．Put up your hands. B．Don’t move or I’ll shoot you. C．If you want to have lunch, you must listen to me. D．You go first slowly and we’ll have lunch together.
A．has a great deal of trouble doing mental arithmetic B．lacks some of the qualities required of a scientist C．just reads about other people’s observations and discoveries D．comes up with solutions in a most natural way