钢筋混凝土、钢丝网混凝土、塑铝混凝土等属于( )。
A.金属材料与非金属材料复合
B.无机金属材料与有机材料复合
C.无机非金属材料与有机材料复合
D.多种复合材料复合
参考答案:A
In this section, we will briefly describe possible ways of reducing the costs and risks ______ in doing this.
A.involving
B.involved
C.to involve
D.being involved
在分子筛含量超过()%时,再增加分子筛的含量,转化率的提高就缓慢得多。
A.4
B.6
C.8
D.10