"Do you hear someone knocking at the door" "Yes, I did. I heard him ______ three times."

A．how to read titles and headings
B．how to find headings in an article
C．what problems to be discussed in science article
D．how to read science material

A．Men worked at a job to earn money for the family.
B．The women made most of decisions.
C．The woman stayed at home to care the children.
D．The man paid the bills.