单项选择题
A．be B．to be C．is D．are
A．Ellsworth Huntington is a fortune-teller rather than a scientist B．cool weather is more effective on man’s creative thinking C．certain elements in nature are more active in one season than in other seasons D．summer is a good season for vacation
A．cost little B．was more expensive than a water system C．was too expensive for every family to afford D．was not necessary