If less than 1.25L of alcohol is used, what is true regarding the final meter reading?

The correct choice indicates that if less than 1.25L of alcohol is used, the air content in the test is always indicated on the final meter reading. This means that the equipment is sensitive enough to detect the presence of air in the sample when the volume of alcohol is below the threshold.

In many measurement processes, especially in liquid analysis, the volume of the liquid can significantly affect the accuracy of the reading. When the liquid is below a certain threshold, such as 1.25L in this case, the equipment may not have enough liquid to create a stable measurement environment, which can lead to the inclusion of air in the reading. Therefore, the meter reading that is obtained will reflect the discrepancy due to the volume being low and capturing both liquid and air, leading to a specific indication of air content.

The other choices suggest either invalidation of the measurement or conclusions about low air content, which are not accurate under the conditions specified. The focus of the correct answer is on the consistent indication of air content when the volume is insufficient, emphasizing the interaction between low liquid volumes and the meter's functionality.