Behavioral regulation of body temperature, like moving closer to the fire, is especially affected by lesions of the
a. lateral hypothalamus.
b. preoptic area.
c. ventromedial hypothalamus.
d. amygdala.

Lateral hypothalamus

Explanation:

The lateral hypothalamus is the part of the brain that is very important in its functioning. The hypothalamus is the small and the central part of the brain. Lateral hypothalamus contains an orexin in the nucleolus of the hypothalamus. It is widely projected in all areas of the nervous system.  

Thus the behavior related to the regulation of body temperature, like moving closer to the fire, is especially affected by the lesion of the lateral hypothalamus.

a would be the answer