题目

 定义两个平面向量的一种运算,其中表示两向量的夹角，则关于平面向量上述运算的以下结论中： ①， ②， ③， ④若则， ⑤若且． 其中恒成立的个数是（ ）． A、5            B、4           C、3                 D、2 答案：D 完形填空 　　I've often puzzled over something that happened to me one winter when I was eight．Over the years I had been wondering if my 　　1　　 was nothing more than a kid's imagination． 　　There was a 　　2　　 near our house．In winter it was the greatest 　　3　　 place in the world．One 　　4　　 all I wanted to do was go skating．I had been waiting for weeks 　　5　　 the water was frozen solid．Mom had one rule：“Never ice-skate alone．” But I couldn't 　　6　　 any longer that afternoon．So I 　　7　　 my skates under my coat and ran to the pond．Several people were skating near the shore, and some kids were playing hockey．I was not really 　　8　　． 　　　The hockey game had attracted 　　9　　 audience, so I skated in the other direction until their cheering 　　10　　．But another noise came soon．The ice was cracking beneath me．Freezing water 　　11　　 my body, and I sank like a rock．My feet 　　12　　 the bottom．Just when I thought I wouldn't last another 　　13　　, I felt a tap on my shoulder．“Don't worry,” someone said．I swung my 　　14　　 around．I couldn't see anybody．But I heard the voice again，“Push your feet into the bottom and you'll shoot straight up to the surface．” I did as I was told and 　　15　　．I crawled to the shore and lay down, 　　16　　．The next thing I knew was people were 　　17　　 around me, covering me with coats．When I awoke, I was home in my own bed．Mom sat next to me, 　　18　　 my hand．“I saw nobody there．It must be an angel that came to my 　　19　　．” I said．Mom smiled, “I just thank God you're safe．” 　　For a long time I thought I would 　　20　　 a more realistic explanation if I just thought hard, but I never did． (1) [　　] A． attention B． behavior C． explanation D． reason (2) [　　] A． river B． pond C． lake D． dam (3) [　　] A． skating B． fishing C． swimming D． skiing (4) [　　] A． afternoon B． morning C． evening D． night (5) [　　] A． after B． until C． as D． if (6) [　　] A． go B． run C． sit D． wait (7) [　　] A． found B． threw C． took D． hid (8) [　　] A． lonely B． single C． alone D． afraid (9) [　　] A． noisy B． happy C． small D． young (10) [　　] A． changed B． disappeared C． increased D． stopped (11) [　　] A． filled B． controlled C． covered D． loaded (12) [　　] A． hit B． dragged C． set D． tapped (13) [　　] A． day B． hour C． minute D． second (14) [　　] A． head B． hand C． arm D． leg (15) [　　] A． left B． succeeded C． tried D． survived (16) [　　] A． worried B． surprised C． excited D． exhausted (17) [　　] A． lying B． standing C． laughing D． crawling (18) [　　] A． raising B． shaking C． holding D． washing (19) [　　] A． place B． mind C． defense D． rescue (20) [　　] A． take up B． make up with C． bring up D． come up with