题目

The field was covered with ____ in the early morning. A.forest          B. frost                C. frown            D. frame 答案：B下列表达中，正确的是（ ）A．饱和氯水中可大量共存Na+、CO32-、SO32-B．溶液中可大量共存Mg2+、HCO3-、SO42-、OH-C．向稀硝酸中加入过量的铁粉：3Fe+2NO3-+8H+=3Fe2++2NO↑+4H2OD．AlCl3溶液和过量浓氨水混合：Al3++4NH3?H2O=Al（OH）4-+4NH4+