-Darkness , so we had to stop our journey and stayed on a farm.
| A．fell | B．spread | C．broke | D．happened. |
This new kind of chemicals will help keep the air, soil and water________ from pollution.
| A．free | B．empty | C．loose | D．short |
Barack Obama has taken personal blame ________ the security failures which led ________ the attempt to blow up a plane on Christmas Day.
| A．of; to | B．for; to | C．on; on | D．in; on |
―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 |
My father didn’t have to say anything. I knew he was upset from his ________.
| A．look | B．sight | C．appearance | D．sign |
Cao Cao’s tomb is reported ________ in China, which attracts nationwide attention.
| A．being found | B．to be found |
| C．having been found | D．to have been found |