Where would a explosive volcano most likely occur

On subduction zones

Explanation:

Explosives volcanoes are most likely to be found on subduction plate boundaries where one plate subducts (goes under) another plate. The subducting plate is usually a plate  made of denser oceanic crust and the upper plate usually consists of less dense continental crust. Because of the composition of the magma and the high silica content found in the continental crust, these eruptions are much more explosive than the gentler basaltic flows characteristics of oceanic hotspot eruptions or undersea divergent plate boundaries.

it would be 2 or b because the clouds are a form of condensation