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He is determining physical properties that are sufficient to identify the metal.

Explanation:

A physical property is an aspect of matter that can be observed or measured without changing it. Examples of physical properties include color, molecular weight and volume. A chemical property may only be observed by changing the chemical identity of a substance.Density, electrical conductivity, and melting point are considered as physical properties and are sufficient to identify a metal as these properties are independent of the  amount of substance being examined.These properties are known as intensive properties and are used  to identify a substance by comparing the obtained values with standard values.

So, the right choice is:

He is determining physical properties that are sufficient to identify the metal.