The purifier is a device in a) - The air separation plant b) - steam power plant c) - - fuel cell d) - refrigerator

a). Air separation plant

Explanation:

The purifier is a device that removes the pollutants or air contaminants from air to improve the air quality in a given space.

There are basically two techniques or ways by which the air purifier makes the air contaminants free. This two techniques are active and passive.

Active air purifiers : negatively charged ions are released to the atmosphere which sticks the pollutants to the surface.

Passive air purifiers : They use air filters to eliminate pollutants and are more efficient than an active air purifiers.

(A) Air separation plant

Explanation:

Purifier is used in air separation plant to purify the air main work of purifier is to remove the pollutants particles from the air and make the air fresh.

On the other hand it has no use team power pant because in steam power plant we don't need to purify the steam and also not used in fuel cell and refrigerator

So purifiers are used in the air separation plant.