题目

质量为m的A球以水平向右的速度V与静止在光滑的水平面上的质量为4m的B球正碰，碰后A球反向，速度大小变为原来的1/2，则碰后B球的速度是  （     ）     A.向右，V/2,    B.向右 ， V/8    C. .向右 ， 3V/8     D. 向左 ， V/8   答案：C解析:略 There is a big ___ in our city. We can see many ___ there. A(n) ___,the biggest animal on land is also living there. Many ___fly in the sky(天空).Some beautiful ducks（鸭子） always ___in the river. What are these in the trees? Oh ,they are ___ .They like ___ leaves. The y are from Australia. Aren’t they cute? There is a tiger in the cage ___ the tree . It eats a lot of meat every day. I like the ___ best because it lives only in China and it is the symbol of___.1.A.park B. zoo C. hall D. school2.A. trees B.students C. food D. animals3.A.lion B. giraffe C.elephant D. cat4.A.birds B. fish C. tigers D. dogs5.A. fly B. swim C. save D.sleep6.A. elephants B. tigers C. koalas D. lions7.A. eating B. eat C. to kill D. killing8.A.on B.in C. under D. over9.A.giraffe B.tiger C .panda D. lion10.A. smart B.scary C. cut D. friendly