A boy opened two packets of milo drink. He left one in the refrigerator and another on the table. Three days later he got a bad smell from the packet left on the table. The packet which was kept in the refrigerator did not have a bad smell. What could be the reason for this?

1. the boy got bad smell from the opened packet left on the table due to rancidity.

2. the packet which was kept in the refrigerator did not have bad smell because they did not come in contact with oxygen.

Explanation:

rancidity - when fats and oils are oxidised they become rancid and their smell and taste changes.

when eatbles come in contact with oxygen they oxidised due to this we get bad smell and taste from it.