For a two post installation, what size wood posts are required for a sign at a specified height above a 10:1 slope?

The correct choice is to refer to plan sheet MT-150.10 because this specific document contains the detailed guidelines and specifications necessary for determining the appropriate size and configuration of wood posts for signage on slopes. Each installation scenario can vary based on different factors such as the height of the sign above ground and the specifics of the slope, which are often outlined in official plans or standards.

Consulting the appropriate plan sheet ensures compliance with safety regulations and best practices, particularly for traffic management and signage installation, where both visibility and stability are essential. Other options like specifying a fixed post height (8-foot or 6-foot posts) do not consider the critical information found in the plan sheet that would provide the most accurate requirements based on site conditions. The last option, indicating no specific size is required, fails to recognize that professional guidance through standard plans is vital for ensuring structural integrity and safety.