近年来,长江洪灾频繁发生,其主要自然原因是( )①中游地区围湖造田 ②中下游地势低平 ③流域内降水丰沛 ④上中游砍伐森林,破坏植被 ⑤支流众多,雨季涨水集中
A:①②③
B:②③④
C:②③⑤
D:①③⑤
—How much do I o____ you, Sir?
—Well, it's $5.50 plus tax. Thank you.
离子方程式2Ca2++3HCO3﹣+3OH﹣→2CaCO3↓+CO32﹣+3H2O可以表示( )