His sister left home in 1998, and _______since.
| A．had not been heard of | B．has not been heard of |
| C．had not heard of | D．has not heard of |
House prices keep rising these days. A flat in our city costs ____ now as in 1990.
| A．as three times much | B．as much three times |
| C．much as three times | D．three times as much |
Make sure that the machine is kept where it is not ____ to children.
| A．possible | B．common | C．accessible | D．Useful |
Mary is the only one of the students in our class who ____ to the Great Wall so far.
| A．is | B．has been | C．are | D．had been |
Two years ago, the 9-year-old girl set up ___ organization named Angel to help ____ homeless.
| A．the; | B．; the | C．an; a | D．an; the |
For miles around me there was nothing but a desert, without a single plant or tree ______.
| A．on earth | B．in sight | C．at a distance | D．in place |