What distinguishes a "Restricted Area" from other types of airspace?

A "Restricted Area" is designated airspace where flight is allowed under specific conditions, which distinguishes it from other types of airspace. Typically, these areas are established for various reasons such as military operations, where the government seeks to limit the access of civilian aircraft to ensure safety and security during sensitive activities.

Pilots can enter these areas with permission or when they are not active, though there are restrictions when the area is in use. This means that instead of being completely off-limits or unrestricted, there are guidelines and procedures that must be followed, which align with the correct answer. The other options do not accurately reflect the nature of restricted airspace, as they either imply total prohibition or lack of any regulations, which is not the case for such designated areas.