只含有一种元素的物质

题干

只含有一种元素的物质（）

A：可能是纯净物也可能是混合物

B：可能是单质也可能是化合物

C：一定是纯净物

D：一定是一种单质

上一题下一题 0.0难度选择题更新时间:2015-02-12 04:31:10

A

The value of time

To realize the value of one year,

Ask a student who has failed a final exam.

To realize the value of one month,

Ask a mother who has given birth to a premature (早产的) baby.

To realize the value of one week,

Ask an editor (编辑) of a weekly newspaper.

To realize the value of one hour,

Ask the lovers who are waiting to meet.

To realize the value of one minute,

Ask a person who has missed the train, bus or plane.

To realize the value of one second,

Ask a person who has survived (幸存) an accident.

To realize the value of one millisecond,

Ask the person who has won a silver medal (银牌) in the Olympics.

Time waits for no one.

Treasure (珍惜) every moment you have.