⑴____ A. grade B. able C. skate D. any
⑵____ A. egg B. me C. went D. tell
⑶____ A. rich B. sister C. swim D. write
⑷____ A. idea B. Korea C. real D. great
⑸____ A. school B. machine C. chemical D. ache
某公园草坪的防护栏由100段形状相同的抛物线形构件组成,为了牢固起见,每段护栏需要间距0.4m加设一根不锈钢的支柱,防护栏的最高点距底部0.5m(如图),则这防护栏需要不锈钢支柱的总长度至少为( )
Don't be worried. You should always look on the bright side of things.
(Ⅰ)求a的值;
(Ⅱ)设函数 g(x)=f(x)−23x3−4lnx+6x ,且g(x1)+g(x2)=0,求证: x1+x2≥2+6 .
下列有关甲苯的实验事实中,能说明侧链对苯环性质有影响的是( )