If you are like most people ,your intelligence   changes with the seasons ,You are probably a lot sharper in the spring than you are at any other time of year . A famous scientist ,Ellsworth Huntington (1876--1947),concluded   from other men's work and his own among people in different climates that climate and temperature have an effect   on your mental abilities  . He found that cool weather is much more favorable for creative   thinking than summer heat .This does not mean that all people are less intelligent in the summer than they are during the rest of the year. It does mean, however , that the mental abilities of large numbers of people tend to be lowest in the summer . Spring appears to be the best period of the year for thinking One reason may be that in the spring man's mental abilities are affected by the same factors   that bring about great changes in nature . 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 . The two best seasons for thinking seem to be   _  .
spring and fall winter and summer summer and spring fall and winter