Question 222General Subjects - 1st Asst/Chief

The correct answer is B) 45 grains of moisture per pound of dry air. This can be determined by referring to the psychrometric chart. Given the dry bulb temperature of 70°F and the relative humidity of 40%, the absolute humidity can be read directly from the chart, which indicates a value of approximately 45 grains of moisture per pound of dry air. The other answer choices are incorrect because they do not accurately reflect the absolute humidity at the specified dry bulb temperature and relative humidity, as shown on the psychrometric chart.