51．A．a piece of paper     B．a message        C．a new story           D．nothing

A

    If you are like most people，your intelligence（智商）changes from season to season．you are probably a lot sharper in spring than you are at any other time of the year．A famous scientist，Ellsworth Huntington （1876-1947）got a result from people’s work and himself．He found our mental abilities（智力能力）would be influenced by different seasons and temperatures．

    He found that cool weather is much better for creative thinking than hot weather．This does not mean that people are not clever in summer．It does mean，however ,that the mental abilities of large numbers of people may be low in summer．   

    Spring seems to be the best time of the year for thinking．In spring all things in nature change．So do our mental abilities．They are influenced and change much，too．

    Fall is the next-best season，then winter．As for summer, it seems to be a good time to take a long vacation from thinking!

50．A．brought           B．broken                 C．gone                D．eaten