中国资产阶级领导的变法和革命失败的根本原因是（）A、儒家思想的传统影响 B、封建顽固

卡介苗是牛型结核分枝杆菌发生下列哪种变异后的产物()

A．毒力变异

B．耐药性变异

C．形态结构变异

D．抗原性变异

E．菌落变异

下列说法中正确的是（　　）

A．绝对值等于其本身的数是0和1

B．有理数分为整数、零和分数

C．如果两个数的绝对值相等，则这两个数相等

D．互为相反数的两个数的绝对值相等

阅读理解填词

       Cannon has shown a great interest in collecting flags. At the young age of four , Cannon began

studying flags , d  1   them in his coloring books and putting them up on his walls Throughout school ,

he studied flags and tried to find out all he could about them After university ,Cannon s  2   to be a

lawyer.Throughout law school , he continued to collect flags His classmates, friends ,and family

started c  3   him "the flagman"

       Cannon now has more than 200 flags in his collection. He shows many of them in his downtown

law office . Once he d  4   country flags for an exhibition on the Olympics

       In addition to collecting flags Cannon also w   5   about them He has published three books about

flags He loves to h  6   from friends who see his b  7   in stores all over the world A few years ago,

Cannon's hobby r   8   a new level He entered a flag design contest and won The country he lives in

asked him to design its f  9    . Cannon explains his hobby this way ,"Collecting flags is l  10    collecting

pieces of history"

如图，a是一列正弦波在t=0时刻的波形曲线，P是波形曲线上的一个质点．b是t=0.4s时的波形曲线．

（1）求这列波的波速；

（2）若这列波是沿x轴负方向传播的，试说出质点P在t=0时刻的运动方向．

由于蜗杆的材料一般为碳钢或合金钢，而蜗轮则常用铸造青铜制造。故蜗轮蜗杆传动失效大多发生在（）上。

A.蜗杆

B.蜗轮

C.轮齿

D.齿面