The scaly skin of snakes serves several important purposes, but one of its primary functions is to protect the snakes from drying out. Here's a detailed explanation of why this is the correct answer:

Protection against dehydration:
- Snakes are ectothermic creatures, which means they rely on external sources of heat to regulate their body temperature. This makes them susceptible to dehydration, especially in dry environments.
- The scales on a snake's skin act as a protective barrier, preventing moisture from escaping their bodies through evaporation. This is particularly important for snakes living in arid regions where water sources may be scarce.
- The scales are tightly interlocked, creating a waterproof layer that helps to seal in moisture and prevent excessive water loss.

Preventing infection:
- In addition to protecting against dehydration, the scaly skin of snakes also acts as a defense mechanism against infection.
- The scales provide a physical barrier against pathogens, preventing them from directly accessing the snake's body.
- The scales also contain antimicrobial properties, which help to inhibit the growth of bacteria and fungi that may come into contact with the snake's skin.

Aiding in locomotion:
- While protecting against dehydration is the primary function of snake scales, they also play a role in aiding the snake's movement.
- The scales provide a low-friction surface, reducing drag as the snake moves across various terrains.
- The scales are also arranged in a specific pattern, which helps to grip the ground and provide traction, enabling the snake to crawl efficiently.

Other functions of snake scales:
- The scales of snakes can vary in size, shape, and texture depending on the species and their habitat. These variations can serve additional functions such as camouflage or thermoregulation.
- Some snake species have scales that are brightly colored or patterned, helping them blend into their surroundings or serve as a warning signal to potential predators.
- The scales on a snake's belly are usually smoother and flatter, allowing for better contact with the ground and aiding in locomotion.

In conclusion, the scaly skin of snakes primarily protects them from drying out by preventing dehydration. However, it also serves other important functions such as preventing infection and aiding in locomotion.

A