Answer:
The correct answer is D. It is incorrect that Southeast Asia can be considered a buffer zone.
Explanation:
In geography, a buffer zone is an area that serves the purpose of keeping two or more areas (often, but not necessarily, countries) at a distance from each other, for any reason. The most common types of buffer zones are demilitarized zones and some restrictive comfort zones and green belts. These areas can be, but not necessarily, composed of a sovereign state, forming a buffer state.
Buffer zones can be created to prevent violence, protect the environment, protect residential and commercial areas from industrial accidents or natural disasters, keeping prisoners with the intention of escaping by quickly acquiring hostages or a hiding place, or possibly by others reasons.
Buffer zones often result in large uninhabited regions (similar to nature reserves, although without tourism) that by themselves are notable in many increasingly paved / busier developed parts of the world.
In the case of Southeast Asia, it cannot be considered a buffer zone, because although it separates Oceania from mainland Asia, there are no political reasons to consider such separation. Likewise, it is a very densely populated area, with its own culture and idiosyncrasies, which go beyond its geographical position.