题目

—________ is it from your home to the train station?   — About 20 miles. A. How far    B. How long     C. How often    D. How old 答案：A下列表示对应化学反应的离子方程式正确的是A．硫化钠溶于水中：S2－+2H2OH2S+2OH－B．醋酸溶解鸡蛋壳：2CH3COOH+CaCO3=Ca2++2CH3COO－+CO2↑+ H2OC．NaHCO3溶液与稀H2SO4反应：CO32－+2H+=H2O+CO2↑D．NH4HCO3溶液与足量的NaOH溶液反应：HCO3-+OH-=CO32-+H2O