混凝土中掺和料有非活性矿物掺和料和活性矿物掺和料，下列哪种属于活性矿物掺和料（）。
A.磨细膜砂
B.石灰石
C.粉煤灰
D.硬矿渣
参考答案：C
No girl likes to make friends with him, _____.[ ]
A. however he is a handsome boy
B. however handsome a boy he is
C. however a handsome boy he is
D. however handsome a boy is he
主机在备车暖机时，最好的暖机方法是（）。
A．将蒸汽直接引入淡水系统
B．利用蒸汽加热冷却水
C．利用电加热器加热冷却水
D．利用副机冷却水
