要鉴别由不锈钢和塑料制成的外形完全相同的两个汤勺。

（1）方法一：_____________________ ，利用了________ 属性；

（2）方法二：______________________，利用了________ 属性。

People often recall having felt chilled before the onset of a cold. This supports the hypothesis that colds are, at least sometimes, caused by becoming chilled; it is the chill that allows a rhino virus, if present, to infect a person. Which of the following, if true, most seriously weakens the force of the evidence cited above

A．Being chilled is a form of stress, and stress lowers the defenses of a person’s immune system, which guards against infection.

B．After a rhino virus has incubated in a person for several days, the first symptom it causes is a feeling of chilliness.

C．People who are tired and then become chilled are more likely to catch severe colds than are people who are chilled without being tired.

D．Some people who catch colds are not sure what it was that allowed them to catch cold.

E．(E) Rhino viruses are not always present in the environment, and so a person could become chilled without catching a cold.