At what measurement does the pressure first reach 1.6" hg?

The question is asking at what measurement the pressure first reaches 1.6 inches of mercury (inHg). In this case, the correct choice is the measurement that directly corresponds to the pressure value referenced in the question.

When pressure is measured in inches of mercury, it is a direct representation of the height of a mercury column that is supported by that pressure. Therefore, when we are looking for the point at which pressure first reaches 1.6 inHg, it is logically the exact value specified in the question.

Thus, the choice reflecting that precise reading of 1.6 inHg is correct because it directly aligns with the pressure being asked about. Other options provide values that either are lower than or do not accurately reflect the 1.6 inHg mark, confirming that the only suitable answer is the one stating 1.6. Understanding this concept of pressure measurement aids in accurately identifying pressure points in industrial refrigeration systems, where readings are often crucial for operational efficiency and safety.