TOEFL Reading: ETS-TOEFL阅读机经 - 3K693IQCYEU94377L$

According to paragraph 4, a bird that flies by alternating between soaring and gliding gains which of the following advantages A. It can often cover short distances faster than it could by flapping its wings to travel. B. It is able to travel a long way without using a lot of energy. C. It can find thermals more quickly than it could by flapping its wings to travel. D. It can stay inside the thermal regardless of how thermal speeds change.