What was the question for this implicit rationale, and corresponding answer?
This is the relevant information: P CO -- Partial pressure of carbon dioxide at sea level (765 mmHg) in arterial blood is between 35 mmHg and 45 mmHg.
 The answer: between 35 mmHg and 45 mmHg
The question: P CO -- Partial pressure of carbon dioxide at sea level (765 mmHg) in arterial blood is between 35 mmHg and 45 mmHg.

Answer this question: the partial pressure of carbon dioxide in arterial blood is approximately?