_______ the smoggy weather, the central government has taken action to deal with it.

There’s someoneknocking on the door Who _________ it be—It must be John He promised to be here at 8:00

The father as well as his three children ___skating on the frozen river every Sunday afternoon in winter.

the radio so that I can hear it clearly.

What is he doing now—He’s ________ the teacher in class now.