下列说法：
①一组对边平行且相等的四边形是平行四边形；
②对角线互相垂直且相等的四边形是正方形；
③顺次连结矩形四边中点得到的四边形是菱形；
④两条对角线相等的梯形是等腰梯形，
其中正确的共有（ ）
A．1个
B．2个
C．3个
D．4个
①一组对边平行且相等的四边形是平行四边形，故说法正确；
②对角线互相垂直平分且相等的四边形是正方形，故说法正确；
③顺次连结矩形四边中点得到的四边形是菱形，故说法正确；
④两条对角线相等的梯形是等腰梯形，故说法正确．
故选D．
| 完形填空。 | |||
| My hobby is playing chess-one of the greatest games in the world．My mum taught me __1__ to play when I was seven years old．She__2__ me every time for the first year．But then, on my __3__ birthday, I won for the first time．Now I am always the winner between us． It takes about a day．To learn tile rules. __4__ if you want to be good,you have to practice for years．You don't need much to play chess. just a chess set and someone to play with． Chess sets __5__ be very cheap,or quite expensive．Some people collect chess sets as a hobby, but I __6__ to play． There is a chess club in my schoo1．We meet every week to play each other．I am the best __7__ in the club, and the captain of the school chess team．This year we __8__ . the all England Schools' Championship (冠军)．I had to go up on stage (舞台) in f  ront of the whole school to collect the prize．I'm saving up my money to buy a chess __9__ ．It's very good for practice．That way I'll __10__ have someone to play with, and I'm sure I'll make more progress． | |||
| ( ) 1． A．what ( ) 2． A．hit ( ) 3． A．seventh ( ) 4． A．And ( ) 5． A．can ( ) 6． A．want ( ) 7． A．player ( ) 8． A．received ( ) 9． A．computer ( ) 10．A．sometimes | B．why B．1ost B．eighth B．So B．must B．wish B．fan B．won B．book B．sometime | C．how C．beat C．ninth C．Yet C．should C．prefer C．1eader C．1ost C．dictionary C．always | D．where D．fought D．tenth D．But D．will D．choose D．learner D．owned D．game D．seldom |