Select the regulatory sign from the options below.

The correct choice is indeed a regulatory sign, which primarily communicates specific laws that drivers must follow. A regulatory sign is designed to inform drivers of the rules and requirements they are legally obligated to adhere to while operating a vehicle.

In this case, the "STOP" sign is a clear example of a regulatory sign because it mandates that drivers come to a complete stop at an intersection or designated area. Failure to obey this sign can result in legal consequences, highlighting its role in maintaining safety and order on the road.

The other options, while they may indicate important information, do not fit the definition of a regulatory sign. A speed limit sign, indicated by the number (35 MPH), suggests a maximum speed but does not enforce an action that must be taken, thus classifying it as an informational sign rather than regulatory. "STOP SIGN AHEAD" serves as a warning to prepare for a stop sign, but it does not convey a direct requirement that must be followed at that moment. Therefore, "STOP" stands out clearly as the sole regulatory sign in the list.