1 . I’m quite sure my keys are in the house. If we just keep seeking, they will certainly ______.

A．turn up

B．take up

C．set off

D．put off

2 . Carbon dioxide emissions (排放) from the burning of energy sources ______ 80 percent of greenhouse gas emissions in the United States.

A．cut down

B．account for

C．add up

D．put on