题目

65. After having failed many times, the young man refused to try it        . A. again and again                         B. once more                   C. less                                       D. over and over again 答案：B下列反应的离子方程式书写正确的是A．氧化铜与盐酸反应O2―+2H＋＝H2OB．二氧化碳通入足量氢氧化钠溶液中：CO2+OH－＝HCO3－C．铝片与硫酸铜溶液反应：2Al+3Cu2+＝2Al3++3CuD．氢氧化钡溶液与稀H2SO4反应：H＋＋OH－＋Ba2+＋SO42－＝BaSO4↓＋H2O