Questions 18 to 20 are based on the following passage. At the end of the passage, you will be given 15 seconds to answer the questions. Now listen to the passage.

What does the well-known joke imply

A．Remarriages often end up in failure.

B．Children are unhappy in the new family.

C．The mother can’t get along with her stepchildren.

D．Remarriages cause new troubles in the household.