纪念戴安娜之死的歌曲《风中之烛》的演唱者是谁？
参考答案：
艾顿庄
A White House plane ________ Beijing on March 19, 2014 and US First Lady Michelle Obama started her ________ visit to China.
A．reached; seven days
B．landed in; seven-day
C．has arrived in; seven-day
D．has got to; seven days
方程2x2-y2=1表示的二次曲面是( )．
A．球面B．柱面C．旋转抛物面D．圆锥面
