Final answer:
The standard mean sea level pressure is 1013.25 millibars or 29.92 inches of mercury, which corresponds to one standard atmosphere. The correct answer is A. 1013.25 mb; 29.92 in. Hg.
Step-by-step explanation:
The standard mean sea level pressure in millibars (mb) is 1013.25, and in inches of mercury (Hg), it is 29.92. Therefore, the correct answer is A. 1013.25 mb; 29.92 in. Hg. The value of 1013.25 mb is equivalent to the average atmospheric pressure at sea level, which is also considered as one standard atmosphere (1 atm). The mercury barometer, which measures atmospheric pressure, would show a column of mercury of approximately 760 mm or 29.92 inches high at this pressure. Meteorologists use these measurements as standard reference points.