Questions 19 to 21 are based on the conversation you have just heard.

A．The style of woman’s sweater can be seen everywhere.
B．The man saw Jill wearing the sweater.
C．She has never worn the sweater before.
D．She seldom borrows Jill’s clothes.

A．To cheek the accuracy of scales.
B．To see the quality of other metals.
C．To measure changes in the air.
D．To measure the length of metal.