Answer: Option A; thick magma with a high level of gases
As the magma increases in temperature, it rises up and gases come out as bubbles on the surface. The pressure of these bubbles is so high that it can exert good amount of pressure on the solid rock surrounding it. This pressure also makes the eruption so violent and explosive. Also magma gets thick due to presence of more silica. So both density and high gas pressure results in an explosive volcanic eruption.
