一个正多边形的每个外角都是36°,这个正多边形的边数是( )
用反证法证明命题:如果AB∥CD,AB∥EF,那么CD∥EF.证明的第一步应是( )
从方框中选出下列各旬的最佳应答语
A.I fell off the bike.
B.No,there weren't.
C.I went there by car.
D.I looked it up on the Internet.
E.Yes,I did.
Once the poison is________,there is no further danger.