— How many people are there in the hall?
— About two ______ people are listening to the speech.
A:hundred of
B:hundreds
C:hundred
D:hundreds of
玻璃仪器洗涤干净的标志是( )
关于城市化的标志,表达不妥的是( )
②2A2++B2=2A3++2B﹣ ③2B﹣+Z2=B2+2Z﹣根据上述反应,判断下列结论中错误的是( )
如图,在△ABC中,∠CAB=∠CBA=30°,AC、BC边上的高分别为BD、AE,垂足分别是D、E,则以A、B为焦点且过D、E的椭圆与双曲线的离心率分别为e1,e2,则1e1+1e2的值为 ( )