Which of the following is an example of homeostasis?

During a time of high stress, Justin's heart races, his muscles tense, and he feels sweat dripping down his forehead.
Sick with the flu, Alison's body temperature rises to fever levels.
Boris doesn't drink very much water one day. To compensate, his kidneys remove less fluid from his blood, and produce less urine than normal.
As Grace races up the ten flights of stairs to her apartment, the muscle cells in her legs produce excess lactic acid, causing a burning sensation in her legs.

Question

Which of the following is an example of homeostasis?

During a time of high stress, Justin's heart races, his muscles tense, and he feels sweat dripping down his forehead.
Sick with the flu, Alison's body temperature rises to fever levels.
Boris doesn't drink very much water one day. To compensate, his kidneys remove less fluid from his blood, and produce less urine than normal.
As Grace races up the ten flights of stairs to her apartment, the muscle cells in her legs produce excess lactic acid, causing a burning sensation in her legs.