探究Mg、Fe、Cu三种金属的活动性顺序,下列试剂的选择方案不可行的是( )
① (1+x)(1−|x|)>0 ;② (x+a)(ax−3a)≤0 .
乾隆时,有人在咏花诗中写道“夺朱非正色,异种也称王”,结果被杀。其门生、印刻者、卖书者、买书者都被判刑。这主要反映了清朝( )
We are all told to take part in the dish—eating up Campaign . So everyone should _____ the dishes they ordered .