Question

magnets are used to close the doors of a refrigerator tightly. give reasons

Answer 1

To make it air tight.
Magnet will firmly keep the door shut so no air will go inside the refrigerator.
And if no air goes inside there will be no spoilage of food.

Answer 2

Magnet keep the door shut and help to form an air tight seal between the door and the refrigerator.
One more reason, to keep children or person safe......