What coded remark would be appropriate for "the prevailing visibility from your point of observation varies from one and a half to two and a half miles"?

The coded remark that indicates the prevailing visibility, especially when it fluctuates between two specific values, needs to convey that variability accurately. In this scenario, the visibility varies from one and a half miles to two and a half miles.

The correct choice includes the indication of the prevailing visibility as "2SM," which identifies the average visibility, and the remark "RMK VIS 1 1/2V2 1/2" which explicitly communicates the range of visibility observed. This remark clarifies to other users of the weather report that the visibility is not constant and provides specific values, enabling them to understand the conditions better.

In contrast, the other answers do not sufficiently convey the variability in visibility. Simply stating "2SM" would not fully inform about the range. "4SM" incorrectly suggests a higher visibility than what is observed, and "1/2SM" significantly underreports the visibility, which could lead to misunderstandings regarding the current weather conditions. Therefore, the coded remark including the range is essential for accurate weather reporting.