About ______ American homes have the habit of keeping pets.

A．Lowering a person's blood pressure.
B．Preparing a young couple for the responsibilities of parenthood.
C．Encouraging social relationships.
D．Indicating the owner's social status and wealth.

A．the index of one's status in a sense
B．part of the accepted cost of a service
C．a reflection of their character
D．a kind of personal attitude