下了有关实验现象或事实叙述错误的是( )
A:切完西瓜的菜刀洗净擦干放在通风干燥处可以防止生锈
B:铁丝在氧气中燃烧,火星四射,生成黑色固体
C:用黄铜片(铜锌合金)和铜片相互刻画,黄铜片上留有划痕
D:将二氧化碳通入燃着的两支高低蜡烛的烧杯中,蜡烛自低到高依次熄灭
m-n=12,则-3(n-m)=( )
— Jim took one-hour ride just now. What a short time he spent finishing such a long way!— He is experienced rider.