A．Examine whether these children were healthy.
B．Find out whether their mothers had smoked.
C．Find why these children suffered breathing problems and lung disease.
D．Look into the effect that mother’s smoking had on their children.

A．The professor might give an exam in class.
B．The man might not be able to leave campus early.
C．The class might not finish their oral presentations.
D．This week’s class might be longer than expected.