题目

足够大的光滑水平面上一小球原处于静止状态.某时刻受到一个向南的1N水平外力作用， 经1s该水平力改为向北而大小不变，再过1s又变为向南而大小不变，如此往复变化， 经9s后撤去此水平外力，该小球的运动情况是（      ）A.时而向南运动，时而向北运动，最后停在原处B.始终向南运动，最后停在原位置以南C.始终向南运动，9s后继续向南匀速运动D.小球的质量未知，无法确定它如何运动 完形填空，阅读短文，从每题所给选项中选出可以入空白处的最佳选项。 　　Today, I felt unhappy with my head full of problems, so I decided to take a walk even though I didn't I know where I would go．The most 　　1　　 thing happened when I was walking along the street． 　　I saw an old man, over seventy years old, sitting on a chair．He was a seller of second-hand shoes．He seemed so helpless and nobody was 　　2　　 his shoes．Then, a little girl came towards him．I heard the girl say in a/an 　　3　　 voice, “Grandfather, may I clean your shoes? ” That old man 　　4　　 and passed her a shoe．The girl said, “I do this 　　5　　 I want to earn some money to buy my brother a new school 　　6　　．” 　　I heard this and tears came to my eyes．To my 　　7　　 , the old man said, “Oh, little girl, just stop doing this．Come with me and I will buy one 　　8　　 you．” To see what would happen, I 　　9　　．They walked to a 　　10　　 and there the old man 　　11　　 got her a uniform, which must have cost him a lot．The girl was 　　12　　 and said, “Thank you so much for doing this．May God bless you．” Then she left, leaving the old man 　　13　　． 　　As the old man decided to leave, I stopped him and whispered in his ear, “You are really a great hero! Thank you for your 　　14　　 ! ” My own sadness had disappeared．It had been 　　15　　 by the light of this moving act．I began to realize that a little act can brighten up someone's day． (1) [　　] A． strange B． unlucky C． amazing D． interesting (2) [　　] A． cleaning B． buying C． finding D． taking (3) [　　] A． polite B． angry C． high D． funny (4) [　　] A． agreed B． sold C． began D． sat (5) [　　] A． if B． unless C． though D． because (6) [　　] A． shoe B． bag C． uniform D． cap (7) [　　] A． sadness B． surprise C． happiness D． excitement (8) [　　] A． for B． to C． with D． at (9) [　　] A． left B． stayed C． guessed D． followed (10) [　　] A． restaurant B． shop C． museum D． sitting-room (11) [　　] A． really B． suddenly C． slowly D． nearly (12) [　　] A． relaxed B． humorous C． tired D． excited (13) [　　] A． crying B． standing C． smiling D． walking (14) [　　] A． money B． kindness C． support D． suggestion (15) [　　] A． driven away B． turned down C． talked about D． used up