Is this the very reason _________ at the meeting for the carelessness and pride in his work?
A.he explainedB.what he explainedC.how he explainedD.why he explained在线课程A
此题具有迷惑性，一看到reason很多同学认为选择D项。解题的关键在于reason作explain的宾语。因此选择A。