The fire must have ______ after the staff had gone home.

A．The doctor can see the man this week.
B．Appointments must be made two weeks in advance.
C．The man should call back on Friday.
D．The doctor canceled his appointments on Friday.

A．She should move the desk back.
B．She should go to the doctor.
C．She should have had someone help him.
D．She should have known the desk was heavy.

A．A new treatment for people allergic to bee stings.
B．A more effective method of preventing bee stings.
C．The use of placebos in treating hypersensitive patients.
D．Bee venom causing fatal reactions in hypersensitive patients.