Which of the following would the nurse expect to include in a community health program designed to control sexually transmitted diseases (STDs)

A. Mass screening of all individuals.
B. Location of the possible sources of infection.
C. Treatment of those with the disease.
D. Isolation of those suspected of having STDs.

His father, who is said to be teaching in Australia, ____ in Nanjing University for more than 10 years.

A．has worked

B．had worked

C．worked

D．has been working