题目

—Have you heard that Tom, along with his parents, _____to Japan? —Really? No wonder I haven't seen him these days.     A．has beenB．has goneC．have beenD．have gone   答案：B  用已知浓度的NaOH溶液滴定未知浓度的醋酸溶液，下列操作中会使测定结果偏低的有（　　）A．以酚酞作指示剂B．锥形瓶沾有少量水C．滴定前，滴定管尖嘴部分有气泡，滴定后气泡消失D．滴定前仰视滴定管读数，滴定后平视刻度读数