How do people react __________ his speech against pollution?
| A．on | B．to |
| C．at | D．in |
The research is so designed that once _______ nothing can be done to change it.
| A．begins | B．having begun | C．beginning | D．begun |
Having a trip abroad is certainly good for the old couple, but it remains _______ whether they will enjoy it.
| A．to see | B．to be seen | C．seeing | D．seen |
_______ such heavy pollution already, it may now be too late to clean up the river.
| A．Having suffered | B．Suffering | C．To suffer | D．Suffered |
Robert is said _______ abroad, but I don’t know what country he studied in.
| A．to have studied | B．to study |
| C．to be studying | D．to have been studying |
The purpose of new technologies is to make life easier, _______ it more difficult.
| A．not make | B．not to make | C．not making | D．do not make |