将 4 mol A 气体和 2 mol B 气体在 2 L 的定容容器中混合并在一定条件下发生如下反应 ：2A(g)+B(g)2C(g)；经 2 s后测得 C 的物质的量浓度为 0.6 mol·L^-1，现有下列几种说法：
① 用物质 A 表示的这段时间的平均速率为 0.3 mol·L^-1·s^-1
② 用物质 B 表示的这段时间的平均速率为 0.6 mol·L^-1·s^-1
③ 2 s 时物质 A 的转化率为30%
④ 2 s 时物质 B 的物质的量浓度为 0.3mol·L^-1
其中正确的是                   （      ）                                 

____个____加上____个____是____个____。

文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（＼）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）.每处错误及其修改均限一词;

2）.只允许修改10处，多者（从第11处起）不计分。

    I once bought the beautiful bracelet from a store and felt excited when I tried it on. Sadly, I was soon disappointed at that my naughty kids broke it. But instead of just feel sad, I chose to repair it myself.

    To my greatly surprise, it didn't take a long time to do it. As time went by, I found that I was not happy with just repairing my breaking bracelets. I started making new bracelets out the materials from my old one. Later on, I  begin to design on my own

    Then I made my first deal. Back in 2013, I posted my bracelets on WeChat for the first time and several friends said that they wanted it. That was just the start. With much materials at hand, I made my designs into reality.