离子交换器出水弧型孔板开孔面积宜为出水管面积的（）倍。
A.1~2
B.2~3
C.1
D.4~6
参考答案：D
The weather was great and the people were friendly—_______ a perfect trip.
A．altogether
B．somehow
C．otherwise
D．anyway
做面包时常用到一种既能减少面粉发酵产生的酸又能使面包松软的白色物质是（ ）
A．食盐
B．小苏打
C．蔗糖
D．烧碱
