设平面π的方程为2x-2y+3=0,以下选项中错误的是()。
A.平面π的法向量为i-j
B.平面π垂直于z轴
C.平面π平行于z轴
D.平面万与xOy面的交线为
参考答案:B
This painting is so valuable that it is rather difficult to calculate _______ its price would be if the museum _______ to sell it.
A.how much; would want
B.what; wanted
C.what; wants
D.how much; wants
下列各装置中,利用电流的热效应工作的是 [ ]
A.电动机
B.电炉子
C.电磁铁
D.发电机