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

A．The man should try to be more understanding.
B．The man’s wife should be more understanding.
C．The man’s negative attitude may be derived from his childhood.
D．The pessimism of man’s wife may be the result of her past experiences.

A．It combines quantitative variables and qualitative variables,
B．It can be used to deal with only quantitative variables
C．It helps to summarize properties of a group of data.
D．It helps to make predictions using a sample of observations.