____ red is a symbol of warmth, it can sometimes make people feel uneasy or even frightened.[ ]

A. As

B. Since

C. If

D. While

以下哪些是底孔导流的缺点（）。

A.钢材用量增加

B.封堵质量会影响坝体整体性

C.可能被堵塞

D.挡水建筑物上部施工受水流干扰