The beneficial effect of oxygen therapy in histotoxic hypoxia is about

**Core Concept**
Histotoxic hypoxia occurs when tissues are poisoned by substances such as cyanide, carbon monoxide, or smoke, which impair cellular respiration and oxygen utilization. In this condition, the body's tissues are unable to use oxygen effectively, leading to a decrease in ATP production and cellular dysfunction.

**Why the Correct Answer is Right**
Oxygen therapy is beneficial in histotoxic hypoxia because it increases the partial pressure of oxygen in the blood, which can help to counteract the effects of the poison. This is achieved through the Bohr effect, where increased oxygen tension shifts the hemoglobin-oxygen dissociation curve to the left, allowing more oxygen to be released to the tissues. Additionally, oxygen therapy can also help to increase the activity of cytochrome c oxidase, the enzyme that is inhibited by cyanide and other histotoxic agents.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because oxygen therapy does not work by increasing the oxygen-carrying capacity of the blood, but rather by increasing the partial pressure of oxygen in the blood and tissues.
**Option B:** This option is incorrect because oxygen therapy does not work by increasing the production of ATP, but rather by providing a substrate (oxygen) that can be used by the cells to produce ATP.
**Option C:** This option is incorrect because oxygen therapy does not work by increasing the clearance of the poison from the body, but rather by counteracting its effects on cellular respiration.

**Clinical Pearl / High-Yield Fact**
In cases of histotoxic hypoxia, the administration of oxygen is crucial, but it should be used in conjunction with specific antidotes such as cyanide kits or methylene blue, which can help to directly counteract the effects of the poison.

**Correct Answer:** C.