TOEFL Reading: ETS-TOEFL阅读机经 - SOD_637J5Z1149HML$

According to paragraph 3, which of the following is Kohler's explanation of the fact that people came together to form villages? A. Combining the population into large villages reduced the negative environmental effects of small social groups. B. As the populations increased, the size of the small social units expanded so much that by A.D. 840 they had grown together forming villages. C. Villages provided the efficient social organization needed to deal with population growth and reduced resources. D. Villages formed on the land cleared by the slash and burn agriculture practiced by small social groups.