Crocodiles store fats in their tail. The tail of a crocodile is specifically designed to store fat reserves. This is because crocodiles are cold-blooded creatures and the fat in their tail serves as a source of energy during periods of low food availability or hibernation.

The head of a crocodile does not typically store fats. It is mainly composed of the skull and brain, which are essential for the crocodile`s survival and sensory perception.

The stomach of a crocodile is responsible for the digestion of food, not the storage of fats. Food is broken down and absorbed in the stomach so that nutrients can be utilized by the crocodile`s body.

Arteries are blood vessels that carry oxygenated blood away from the heart. They are not involved in the storage of fats in crocodiles or any other animal.

Therefore, the correct option is 3 - tail. The tail of a crocodile is adapted for fat storage and plays an important role in providing energy for the crocodile during times of scarcity.