题目

In the reading room, we found her _______at the desk, with her attention ______on a book. A. seated; fixing    B. to sit; fixed  C. seated; fixed       D. seating; fixing 答案：C关于Na2CO3与NaHCO3的性质判断正确的是( )A．常温下溶解度：Na2CO3＜NaHCO3 B．热稳定性：Na2CO3＜NaHCO3C．与同浓度同体积的盐酸反应的速率：Na2CO3＞NaHCO3D．与澄清石灰水反应，均有白色沉淀生成