Animals burrow into deep layers of soil in winter because it is
A. Very cold
B. Rich in gold
C. Warm
D. Safe

Hint: The atmosphere of the upper part around ten centimeter of the ground is a few degrees hotter than the atmosphere of the air.

Complete answer:
Hibernation causes lower body temperature, slower breathing and a lowered heart rate as well as diminished metabolism. Hibernation is a reaction for activity in changing seasons. While mammalian hibernation is frequently related to increases in the abundance of resources as a result of cold temperatures, hibernation in amphibians and Reptiles is most likely a direct reaction to cold temperatures and consequently changes in availability of resources.

As winter in temperate areas is coming, most amphibians and reptiles are finding protection where environmental minimum temperatures are not below zero. Some amphibians and tortoises escape subfreezing by wintering on the lakes and streams.

Burrowing hibernators must cope with sustained cold and hunger by fuel reserves accumulation and metabolic rate change. Burrows in hibernation must prevent desiccation, conserve heat, protect against predators, provide environmental markers to cause an increase and sustain a level of oxygen. Therefore, Animals burrow into deep layers of soil in winter because it is warm.

Thus, the correct answer is option ‘C’. i.e., warm.

Note: Most insects and other invertebrates spend the winter hibernating, because it is too cold to become involved so they don't produce their own body fat. But 10 cm below the ground, the atmosphere is always a few degrees hotter than the air and many soil species live under the soil.