Where do tectonic activities, such as earthquakes or volcanic eruptions, tend to occur?
a-near plate boundaries
b-near all mountains
c-in the center of continents
d-only on the ocean floor

a-near plate boundaries

Explanation:

The plate boundaries form the basis for the tectonic activity and due to this the plate collides and the there collision results in the formation of the volcanoes as they are bent and overthrust by the underlying material and enhance the occurrence of the earthquakes take place here, like this in an active margin of the two plates either the oceanic or the continental plate. The plates collide and form a mountain when its continental in origin while formation volcano of its oceanic and the continental plate, and the earthquake ate bound to occur due to this. The tectonic activity thus depends on the rock movement from below and the intensity of the pressure and the release of force form the convective center of the earth.  

Yes that is correct answer in 6

Answer (d) may increase or decrease porosity through dissolution or deposition;