Final answer:
The question relates to the required fire-resistive rating of exterior walls in dwellings with fire sprinkler systems based on fire separation distance, which is typically 5 feet according to the IBC, but another figure must be selected from the options provided in the absence of this choice.
Step-by-step explanation:
The question pertains to the fire-resistive rating required for exterior walls of dwellings with fire sprinkler systems when the fire separation distance is below a certain threshold. While specific building codes can vary by jurisdiction, the International Building Code (IBC) and similar regulations typically require that exterior walls with a fire separation distance of less than 5 feet must have at least a one-hour fire-resistive rating with exposure from the outside. However, as the question does not provide this as an option, and considering standard practices and close proximity issues, the nearest available option would be 5 feet. Nevertheless, since this option is not listed, it is advised for the student to refer to the local building codes or the specific code book referenced in their coursework to determine the correct threshold value.
To clarify, the code might establish, for example, that for any fire separation distance below 5 feet, a one-hour rating may be required. If the choices provided were 10, 15, 20, or 25 feet, one would need to select the most applicable option based on the most conservative approach, or the lowest number which is 10 feet. However, without additional context or guidance from the relevant building code, it's important to check the specific code requirement to confirm.