All regulatory road signs can be categorized into

All regulatory road signs can be categorized into prohibitive and mandatory. Prohibitive signs are designed to prohibit or restrict certain actions on the road. Examples of prohibitive signs include "No Entry", "No Parking", and "No U-Turn". These signs indicate actions that are not allowed on the road. Mandatory signs, on the other hand, are designed to provide instructions to road users on what they must do. Examples of mandatory signs include "Keep Left", "Stop", and "One Way". These signs indicate actions that are required of road users. Therefore, the correct option is "prohibitive and mandatory".