题目

如图所示，固定在竖直平面内的光滑圆弧轨ABCD，其A点与圆心等高，D点为轨道最高点．DB为竖直线，AC为水平线，AE为水平面．今使小球自A点正上方某处由静止释放，且从A点进入圆轨道运动，只要适当调节释放点的高度。总能保证小球最终通过最高点D，则小球在通过D点后    (    ) A．一定会落到水平面AE上B．一定会再次落到圆轨道上C．可能会落到水平而AE上D．可能会再次落到圆轨道上  37、We have two new students in our school. They are Mike and Tim. They look the same, but they are not twins（双胞胎）. Mike is American. He is twelve. He is in Class Four, Grade One. He has a little sister. He often（常常）looks after her. Tim is Canadian（加拿大人）. He is twelve, too. He is in Class One, Grade One. He likes football. He often plays football with us. Mike and Tim are good friends. They are in No. 10 Middle School. （   ） 1. Mike is _______.   A. Japanese          B. Chinese       C. Canadian             D. American （   ） 2. Mike often _____ his sister.    A. looks like          B. looks after      C. looks at               D. looks the same （   ） 3. Mike and Tim are in _____. A. the same（相同的） class           B. the same school C. different grades                    D. different schools （   ） 4. Who likes football? A. Tim.             B. Mike.            C. Tim and Mike.     D. No one. （   ） 5. Which is right?  A. Mike is thirteen.                       B. Tim often looks after his little sister. C. Mike and Tim are good friends.        D. Mike and Tim are twins.