Which best describes a compound such as sodium chloride?
a pure substance that can be separated into different elements by physical means
a mixture of two common substances that can be separated by chemical means
a mixture of two common elements that can be separated by physical means
a pure substance that can be separated into different elements by chemical means

The second option is the answer.  This is a mixture of two common substances that can be separated by chemical means.

NaCL is a compound that was formed through a chemical  reaction between sodium and chlorine. In that reaction sodium  which is a toxic metal combines with chlorine, a poisonous gas, to form a harmless but totally new compound NaCl or table salt.

Since the sodium ions have a positive charge and the chlorine ions have a negative charge, they are attracted to each other to form an ionic bond. 

 Sodium can only be separated from Chloride by chemical means e.g.  electrolysis.

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.