题目

下列反应的离子方程式正确的是                                                               （    ）       A．金属铝溶于稀稍酸中：       B．纯碱溶液显碱性的原因：       C．将少量的硝酸银溶液滴入碘化钠溶液后，再滴加硫化钠：       D．Ca（ClO）2溶液中通人过量的二氧化硫气体：Tim’s sister ______ as a waitress in a big restaurant for the time being.A. was working B. worked C. has worked D. is working