It is only in recent years that people have begun to know about wind power.

A．the Great Depression took place
B．they were no longer self-sufficient
C．the Agriculture Adjustment Act was unconstitutional
D．unfavorable weather conditions brought about crop losses

A．people throw away expensive CDs and audio cassettes
B．listening to music on the go becomes less convenient
C．people can't select their music at random
D．people can't appreciate high quality music any more