Why are some volcanoes explosive while others are not?

There are actually very few volcanoes that do not explode, but the ones that do explode with a high sound and lots of hot magma, and some are very low and don't have a lot of magma. An explosive eruption always begins with some form of blockage in the crater of a volcano that prevents the release of gases trapped in highly viscous andesitic or rhyolitic magma. The high viscosity of these forms of magma prevents the release of trapped gases.

the correct answer is b

i think that it is plants