聽短文，選擇正確答案．
（1）Scientists want to change_____into field land．
 A．desert
B．forest
C．sea
（2）_____land is becoming desert．
A．Less and less
B．More and more
C．Fewer and fewer
（3）_____prevent the wind from blowing the dirt away．
A．Rain
B．Desert
C．Plants
（4）Scientists _____change the desert in a short time．A．can't
B．may
C．ought to
（5）Scientists think people_____bad things to the earth．
A．did
B．will do
C．a(chǎn)re doing