—People near the lake didn't allow them to________ a factory so as not to pollute the water.
A:look up
B:put up
C:take up
D:set up
魏晋时期,选拔官员的主要标准是( )
下列六种说法正确的个数是( )
①无限小数都是无理数;
②正数、负数统称实数;
③无理数的相反数还是无理数;
④无理数与无理数的和一定还是无理数;
⑤无理数与有理数的和一定是无理数;
⑥无理数与有理数的积一定仍是无理数.