Chen:

A．To explain why recycling important.
B．To describe the recycling program.
C．To discuss whether or not recycling should be mandatory (命令性的).
D．To explain how to find the recycling facilities.

A．Speed limits are the same in all areas.
B．She’d told him what it was.
C．There are signs along the road.
D．He has recently received his driver’s licens