Can protected airspace touch each other?

Protected airspace can indeed touch each other. This is important for understanding how different airspace classifications interact and co-exist. For example, controlled airspace like Class B, Class C, and Class D can adjoin or overlap with other types of airspace, such as special use airspace or even uncontrolled airspace.

When designing airspace structures, it's common for sectors to be designed in a way that their boundaries can touch, allowing for efficient management of both controlled and uncontrolled operations without compromising safety. This allows for the smooth transition of aircraft from one type of airspace to another while maintaining necessary safety clearances and communications.

The concept of touching airspace does not necessarily imply a need for vertical separation, as long as the airspace classifications are clearly defined and managed according to regulations. Other options signify different possibilities that do not apply here.