If prevailing visibility is two miles, but it is one and one-half miles to the south, how would that be reported?

The correct reporting of prevailing visibility includes both the overall visibility and any significant variability that could impact pilot operations. In this scenario, the prevailing visibility is two miles, which is the distance visibility is clear in general terms. However, since visibility is specifically noted to be reduced to one and one-half miles to the south, this detail needs to be included in the report as it indicates a significant condition that could be relevant for navigation and safety.

The correct answer highlights the prevailing visibility as "2SM," indicating two statute miles, while the remark "RMK VIS S 1 1/2" provides additional clarity regarding the reduced visibility to the south. This format is standard in meteorological reporting, allowing for both the primary visibility and any notable reductions to be easily understood by observers and pilots.

Including both elements ensures that the report is comprehensive and conveys all necessary information for safe flight operations. The other choices either omit part of the required information or do not clearly convey the same level of understanding regarding visibility.