________ 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

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

Unless ________ to speak, you should remain silent at the conference．

A．invited

B．inviting

C．being invited

D．having invited

________ the meeting himself gave them a great deal of encouragement.

A．The president will attend

B．The president to attend

C．The president attended

D．The president’s attending

The man we followed suddenly stopped and looked as if ________ whether he was going in the right direction．

A．seeing

B．having seen

C．to have seen

D．to see

The manager, ________ his factory’s products were poor in quality, decided to give his workers further training.

A．knowing

B．known

C．to know

D．being known

The new dictionaries are very useful．They________ well and ________ already.

A．sell; have been sold out

B．sold; had sold out

C．sell; sell out

D．are sold; have been sold out

I meant to ________ the camera along, but I forgot, so we went and ________ it.

A．bring; took

B．take; carried

C．fetch; brought

D．bring; fetched

________ that they can pass the written exam this time.

A．They are hoped

B．It is hoped

C．That expects

D．It is told