Refer to figure.
CARBON MONOXIDE POISONING

Carbon Monoxide (CO) is produced by the incomplete combustion of Carbon in fuel. It is a flammable gas that does not have any colour, smell or taste. Carbon monoxide is highly toxic with cumulative effects. It could enter the flight compartment due to a cabin heater leak (bleed leak) causing several symptoms. Modern aircraft systems can detect carbon monoxide in the air.

When breathing in carbon monoxide, it interferes with the red blood cells mixing with hemoglobin 210 to 250 times better than oxygen. This means that oxygen can no longer mix with hemoglobin and there will be a lack of oxygen delivery to the body tissues. Symptoms of carbon monoxide poisoning include headache, nausea, dizziness, sore throat, dry cough, loss of muscular power, impaired judgment and loss of consciousness.

Let's analyze the given options:

A decrease or a loss of muscle power. → CORRECT. Carbon monoxide reduces oxygen delivery to tissues. Muscles (and the brain) are highly sensitive to low oxygen and loss of muscular power occurs.

Increased visual acuity. → INCORRECT. Carbon monoxide causes visual disturbances, such as blurred or tunnel vision. Vision becomes worse, not better.

Intense itching of the skin. → INCORRECT. Carbon monoxide symptoms are mainly related to oxygen deprivation, not skin irritation.

Improved decision-making skills. → INCORRECT. Carbon monoxide poisoning impairs the brain, causing confusion, poor judgment, slower thinking. Decision-making becomes worse.