Which statement best describes two events that occur at a convergent boundary where one plate moves under another a. frequent earthquakes may occur volcanic activity may be common b. it will be rare for earthquakes to occur and volcanic activity will be minimal c. earthquakes will be frequent but volcanic activity will be maximum d. a trench may fork but earthquakes and volcano activity will be minimal

A. Frequent earthquakes may occur volcanic activity may be common.

When the plates of the continents and oceans collides, the thin and dense oceanic plate submerged under the thick and less dense continental plate. This process is called as subduction. As the oceanic plate submerged down the earth crust it is exposed to the hot magma. The melting of the subducted plate occurs and this results in the high intensity volcanic eruption and  frequent earthquakes.  

it should be p1 v1 = p2 v2

if you mean hydrogen and oxygen then water is the product