The ph of a solution is 7. when acid is added to the solution, the hydronium ion concentration becomes 100 times greater. what is the ph of the new solution? a) 14 b) 9 c) 1 d) 5

It's D <<<<
For every power of 10, the pH goes down 1. 7 is neutral. As you add acid, the pH will decrease. 

If you start out with a pH of 7 and you add a base the pH will go up. That's practically the only rule you need.

That result from subduction of oceanic plates beneath lighter continental plates. most of the earth's volcanoes are located around the pacific ring of fire because that the location of most of the earth's subduction zones.