TOEFL Reading: ETS-TOEFL阅读机经 - 753T0QNNRBX14E18L$

Which of the following can be inferred from paragraph 4 about how bank swallows find food cooperatively? A. They give special favors to members of their community that have been successful foragers. B. They use special calls and signals to indicate to other swallows where food is located. C. They observe the direction a successful forager took to locate prey. D. They locate concentrations of prey by setting off in different directions.