Questions 19 to 22 are based on the conversation you have just heard.

A．The child’s brain is highly selective.
B．The faculty of speech is inborn in man.
C．Children do not need to be encouraged to speak.
D．Most children learn their language in definite states.

A．The Thames has not been saved from pollution yet.
B．The condition of the Thames was at worst in the 1950s.
C．Few people are concerned about the pollution problems of the Thames.
D．No one is certain what the main cause for the pollution of the Thames is.