河流入海口通常是港口发育的理想场所,但黄河入海口却没有形成港口,主要的自然原因是什么?
参考答案:
①黄河改道频繁,河口位置不稳定;②河口泥沙淤积严重,航行条件差。
—Mum, could I have an MP3 like this?
—Certainly, we can buy _______ one, but as good as this. The price of this kind is a little high. [ ]
A. a cheap
B. a cheaper
C. a small
D. a smaller
旋毛虫病患者水肿的特点是()
A.发生在双下肢
B.约80%的病人出现
C.进展迅速
D.持续2周左右
E.发生在眼睑、颜面、眼结膜