两台设备利用红外传输的有效操作距离是（）。
A.10米
B.5米
C.1米
D.20米
参考答案：C
某医师在研究工作中分析两个变量的相关回归关系，算得的统计量是：∑(x -)2=45.2，∑(y-)2＝78.8，∑(x-)(y-)＝-55.6，∑(-)2＝82.7，这里有错误的是统计量中出现了（）
A.A
B.B
C.C
D.D
E.E
On Children’s Day, of the students was pleased because they each a present.
A．every one; was given
B．everyone; was given
C．every one; were given
D．everyone; were given
)2=45.2，∑(y-
)2＝78.8，∑(x-
)(y-
)＝-55.6，∑(
-
)2＝82.7，这里有错误的是统计量中出现了（）