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．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.