下列实验中金属或金属氧化物可以完全溶解的是( )
A:常温下将64g铜片投入过量浓硫酸中
B:向100.0mL 3.00mol/L的稀硝酸中加入5.6g铁
C:1mol MnO2粉末与含4mol HCl的浓盐酸共热
D:常温下1mol铝片投入20.0mL 18.40mol/L硫酸中
如图,动点O从边长为6的等边△ABC的顶点A出发,沿着A→C→B→A的路线匀速运动一周,速度为1个单位长度每秒.以O为圆心、3为半径的圆在运动过程中与△ABC的边第二次相切时是点O出发后第____ 秒.
下列几种化学元素和生命活动关系的叙述,不正确的是( )
We have made a survey among 1,000 students from a middle school about their favorite food. students like fruits according to the form.
Kind of food
Chocolate
Banana
Cookie
Apple
Percentage(百分比)
Of the students
20%
30%
15%
?