Which of these is an example of a reversible physical change?
a) boiling water
b) breaking glass
c)cracking an egg
d) splitting a diamond

A) boiling water is your answer.

This is a reversible physical change, for you can cool down the temperature, which would cause condensation of the water, returning it to liquid state.

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i'm assuming that it's c.) red bank..

the electrical  conductivity  of asolution  of an electrolyte is measured by determining the resistance of thesolution  between two flat or cylindrical electrodes separated by a fixed distance.