- Do you know the boy in blue?- Yes. I ________ him several times since last month.

题干

- Do you know the boy in blue?

- Yes. I ________ him several times since last month.

A：meet

B：have met

C：am meeting

上一题下一题 0.0难度选择题更新时间:2019-07-23 11:59:47

B

	实验事实	结论
①	将等浓度的盐酸、碳酸氢钠两溶液混合反应，产生CO₂气体	非金属性：Cl＞C
②	将燃烧的镁条放入CO₂中能继续燃烧，产物有C	还原性：Mg＞C
③	MgCl₂、AlCl₃溶液中分别加入过量氨水，均产生白色沉淀	金属性：Mg＞Al
④	某无色溶液中加入氢氧化钠溶液并加热，产生的气体能使湿润红色石蕊试纸变蓝	该溶液中一定有NH₄⁺