―Look! What a mistake! Why?
―Sorry, I _________ on it.
| A．don’t concentrate | B．hadn’t concentrated |
| C．haven’t been concentrating | D．wasn’t concentrating |
It is commonly assumed that the growth of GDP and the development of people’s living conditions are not _______cause and effect.
| A．nearly | B．possibly | C．purposely | D．necessarily |
—How much is too much for a schoolbag?
—Experts say students should carry_______ more than 10 or 15 percent of their body weight.
| A．no | B．not | C．any | D．far |
Although the huge engine, as tall as 25 meters, is heavy_______, it is powerful and works well.
| A．carried | B．to be carried | C．to carry | D．being exposed |
Some people haven’t realized something as common as _______to the sun for a long time will do harm to their skin and even cause skin cancer.
| A．exposing | B．being exposed | C．having exposed | D．exposed |
He travelled to many mountains and saw many poor children, which _______his life.
| A．would change | B．had changed | C．was to change | D．was changing |