Choice A rationale:

Feeling tired and weak is a common symptom of polycythemia due to the increased viscosity of the blood.

However, this is a general symptom and not specific to polycythemia alone.

Many conditions can cause fatigue.

Choice B rationale:

Red and flushed skin is a characteristic sign of polycythemia.

Increased red blood cell count can lead to increased blood flow to the skin, resulting in a flushed appearance.

This is a specific symptom of polycythemia and should be assessed during the physical examination.

Choice C rationale:

Frequent nosebleeds can occur in polycythemia due to increased blood viscosity and pressure on blood vessels.

This is another specific symptom that should be assessed in a patient with suspected polycythemia.

Choice D rationale:

Shortness of breath can also be a symptom of polycythemia, especially when there is an excessive increase in red blood cells.

However, like fatigue, it is not specific to polycythemia and can be caused by various respiratory and cardiac conditions.