The authors mentions all the following as causes of declines in population growth after 1957 EXCEPT
A. people"s staying at school longer.
B. people"s getting married earlier.
C. better standards of living.
D. couples" buying houses before starting families.
Which of the following is CORRECT？
A. The climate in the south and north is very terrible.
B. Southern Americans suffer a lot when it is very hot.
C. Many lakes and rivers make the transportation chaotic.
D. Transportation by water is less important than before.
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