选A,这里省略了引导词that.the reason (that) he explained at the meeting...你说的改为正常语序是说改为陈述句吧?改为陈述句就是This is the reason (that) he explained at the meeting for his carelessness in ...那句意不变，怎样改为定语从句，还有怎样改为what he explained的形式再请问主语怎样提前谢谢这里面已经含有一个定语从句，that he explained...in his work就是定语从句，修饰reason。如果改为what he explained那就把the reason去掉，因为what=all that：Is this what he explained at the meeting for his carelessness in his work?Is this what he explained at the meeting for his carelessness in his work?的陈述句式是？？This is what he explained at the meeting for his carelessness in his work.