题干
At the end of the meeting, it was announced that an agreement ______.
A：has reached
B：had reached
C：has been reached
D：had been reached
答案(点此获取答案解析）
D
At the end of the meeting, it was announced that an agreement ______.
A：has reached
B：had reached
C：has been reached
D：had been reached
3C(g)＋D(g)，达到平衡时C的浓度为W mol·L－1。若维持容器体积和温度不变，按下列四种方法改变起始物质及其量，达到平衡后C的浓度仍为W mol·L－1的是( )