The more you give, ______ you obtain.

A．Information in short-term memory is different from that in long-term memory.
B．Long-term memory can be achieved only by training.
C．It is easier to test short-term memory than long-term memory.
D．Henning gave a separate test on vocabulary to his students.

A．It is difficult to prevent forest fires.
B．Smoking is allowed only in certain forests.
C．11% of the forest fires in the Western States are caused by lightning.
D．Experiments in "seeding" thunder clouds have helped reduce lightning-caused forest fires.