The number of people ________ this happens is not very large.
| A．with whom | B．to which | C．to whom | D．on which |
The old sick lady entered the hospital, ______ her two sons.
| A．to support | B．supporting | C．supported by | D．having supported |
_______ many times, he still couldn't understand.
| A．Having been told | B．Having told | C．He having been told | D．telling |
Many things _______ impossible in the past are very common today.
| A．consider | B．considering | C．considered | D．be considered |
The students in the university are all taking courses _______ a degree.
| A．coming to | B．going to | C．leading to | D．turning to |
. _______ different kinds of pianos, the workers farther improved their quality.
| A．To produce | B．Being produced | C．Produced | D．Having produced |