Answer:
The boundary is between the African Plate and the Eurasian Plate.
Step-by-step explanation:
The boundary that is marked with the arrow is the one between the African tectonic plate and the Eurasian tectonic plate. Both of these plates are continental plates, bearing the two largest continents on Earth. The African Plate and the Eurasian Plate collide thus they have a convergent boundary.
This convergent boundary is very complex, as it is not just the interaction between the two plates, but on both sides, there are hundreds of miniature polygonal pieces of crust, intersected on all sides, and they are highly active. The African Plate is moving toward the northeast, while the Eurasian Plate is moving toward the southeast. Because of the interaction between these two plates, there are numerous mountain ranges, some large, some smaller, close to their boundary, and the area is tectonically highly active, with multiple active volcanoes and a lot of earthquakes.