What area within the runway can be used to taxi but not for landing?

The threshold area refers to the beginning of the runway that is designated for landing aircraft. It indicates where the runway starts and is used by aircraft during their landing approach. While the threshold signifies the starting point of landing operations, it is not meant for taxiing.

In contrast, the other choices have different purposes. The clearance area is usually designed for safety and prevents obstacles, while the burst zone is a safety area for overruns. The taxiway area specifically allows for movement of aircraft on the ground but is distinct from the runway, highlighting its function as a pathway for aircraft to move between different points without being used for landing or takeoff.

Thus, the designations in these areas are crucial for maintaining safe and efficient airport operations, clearly separating where aircraft can taxi from where they are to execute landings. Consequently, the threshold cannot be used for taxiing, making it the correct focus when identifying an area that allows taxiing but not landing.