单项选择题
A．a scientist as well as a naturalist B．a naturalist but not a scientist C．no more than a born naturalist D．first of all a scientist
A．full of ambition B．knowledgeable C．full of enthusiasm D．self-disciplined
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