---Our environment is worse and worse. What should we do ? ---Can you________ some ideas to deal with the problem? A. think up B. cheer up C. clean up D. set up 答案:A下列命题中:①有理数是有限小数;②有限小数是有理数;③无理数都是无限小数;④无限小数都是无理数;⑤一个数的算术平方根一定是正数;⑥一个数的立方根一定比这个数小.其中正确的有( )
A、2个B、3个C、4个D、5个