Answer: Adrenal glands
Step-by-step explanation:
Adrenal glands are located above each human kidneys these glands secrete hormone adrenaline during stress conditions or during emergency.
Here, Beth is stressed about her test so she finds her classroom warm and an urge for thirst has also arise due to her being this is a kind of stress response generated by the adrenal glands and their secretions in the form of adrenaline hormone.