________ it comes to the increasing use of motor vehicles in the cities，some people think it should be limited．
| A．Because | B．Once | C．When | D．While |
What worried the child most was ____ to visit his mother in the hospital.
| A．his not allowing | B．his not being allowed |
| C．his being not allowed | D．having not been allowed |
The baby cried again. The young mother felt very ____ and her husband wore ____ expression on his face, too.
| A．confused; confused | B．confusing; confused |
| C．confusing; confusing | D．confused; confusing |
There is ____ Mr. Smith at the door who wants to speak to you.
| A．a some | B．certain | C．some a | D．a certain |
. To make sure that he was at home, I called him up ____ .
A. by chance B. in general C. in particular D in advance
In face of ____ failure, it is the most important to keep up ____
good state of mind.
| A．不填, a | B．a, 不填 | C．the, a | D．不填, the |