离心泵倒转的原因是（）。
A、电源正负极接反
B、电源的相位排序错误
C、电源的电压等级错误
D、电机线圈绕组不对
参考答案：B
The Hotel Al Arab ______ the first and only 7-star hotel in the world was designed in the
shape of a sail of 321 meters.
A．was considered
B．considering
C．being considered
D．considered
可观测宇宙大于“宇宙寿命乘以光速”。（）
