[单项选择]During the rainy season the Mississippi River may carry away hundreds of acres of valuable top soil from one area and arbitrarily deposit it in another.
A. subsequently
B. lawfully
C. mercilessly
D. randomly

[单项选择]During the rainy season the Mississippi River may carry away hundreds of acres of valuable topsoil from one area and arbitrarily deposit it in another.
A. subsequently
B. lawfully
C. mercilessly
D. randomly

[单项选择]

Your intelligence varies from season to season if you are like most people. You are probably much sharper in the spring than you are at any other time of the year. A famous scientist, Ellsworth Huntington, concluded from other men’s work and his own among peoples in different climates that climate and temperature have a definite effect on our 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 most 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 men’s mental abilities are affected by the same factors that bring about great changes in all nature.
Fall is the next-best season, then winter. As for summer, it seems to be good
A. records of changes in his own intelligence
B. work with people in different climates
C. records of temperature change
D. all of the above