Questions 11 to 18 are based on the conversation you have just heard.

A．Pollution of the environment.
B．A new generation of pest killers.
C．Over-killing by hunters.
D．Destruction of their natural homes.

A．Only one out of four girls cries less often than boys.
B．Of four boys, only one cries very often.
C．Girls cry four times as often as boys.
D．Only one out of four babies doesn’t cry often.