Today is my birthday. I am a girl. My name is Han Mei. I'm nine years old. I have a birthday party. I have a birthday cake and many gifts. My father and my mother say“Happy birthday!”to me. I'm very happy.
May I have a pie, please?
关于黄土高原水土流失原因,正确的是( )
①水量丰富,年降水量800毫米以上;
②土质疏松;
③植被稀少,地面缺少植被的保护;
④过度放牧,不断开垦种地等人类活动加剧.