Using a declinated M2 or a lensatic compass, the observer can measure direction to an accuracy of how many mils?

The correct answer reflects the precision associated with using a declinated M2 or a lensatic compass for measuring direction. When utilizing these compasses, observers can accurately measure direction down to 10 mils. This level of accuracy is important for military operations where precise targeting and navigation are critical, especially over varying distances.

The reference to 50 meters indicates that the accuracy is further impacted by range, meaning that at distances up to 50 meters, the measurement remains sufficiently precise for operational effectiveness. This highlights the usability of such compasses within a tactical environment where rapid and accurate direction finding is essential.

While other options present varying degrees of accuracy and distance, they do not align with the established capabilities of the M2 and lensatic compasses used in the field. Thus, the chosen answer effectively represents the standard measurement accuracy and distance limit applicable in such scenarios.