TOEFL Reading: ETS-TOEFL阅读机经 - I68DRX71Y948SVQLL$

According to paragraph 4, which of the following may have helped push the Natufians toward farming as a way of life A. At the same time as the Natufian population was increasing, the climate was becoming less hospitable. B. The development of sickles and other tools made it possible for Natufians to exploit new kinds of cereals. C. The climate changed during the Natufian period and produced conditions favorable to growing cereals. D. Increasing competition from neighboring populations may have forced Natufians to grow cereals more intensively.