The correct answer is - lava dome.
The lava dome represents a circular mound-shaped protrusion which is a result of a highly viscous and slow magma coming up in a larger volcano. Because it is very highly viscous, this type of magma cannot move far away from the volcano and usually builds up. The high viscosity can be as a result of either degassing of the fluid magma, or from a very high content of silica in its structure. Around 6% of the eruptions in the world create lava domes, usually in convergent plate boundaries.