仲裁裁决可能因（）而无效。
A.一方缺席
B.仲裁协议无效
C.仲裁法庭越权
D.仲裁员有欺诈行为
E.首席仲裁员受威胁
参考答案：B, C, D
如果{2，3，4}={2，x，3}，则x=______．
The reason _____ he failed the exam was that he spent more time playing and less time learning. [ ]
A. because
B. that
C. why
D. which
