30. He _____ his potential had it not been for his desire to meet new challenges.
| A．would never have realized | B．would never realize |
| C．never realized | D．had never realized |
The policeman came up to the lonely house with the door open, ________ there for a while and 
then entered it.
| A．stood | B．standing | C．to stand | D．having stood |
Either she or I ________ going to give a lecture to the students after class.
| A．are | B．am | C．is | D．has |
_______ the crisis of economy (经济危机) getting more and more serious, the government is searching for ways to improve people’s life.
| A．As | B．With | C．When | D．If |
Eating too much fat can ________ heart disease and cause high blood pressure.
| A．result from | B．contribute to | C．attend to | D．lead in |
My son isn’t feeling well, so I’ll get him ________ in the hospital.
| A．examined | B．examining | C．to examine | D．examine |