太行山山以东的地形区是（）
A．黄土高原
B．云贵高原
C．华北平原
D．长江中下游平原
参考答案：C
With ____ leaves ____ in the earth every year, the soil becomes richer and richer.
A．falling; burying
B．fallen; buried
C．fallen; burying
D．falling; buried
