Sulfur has an atomic number of 16. how many covalent bonds can sulfur form?

Two because it has six electrons in it's valence shell and it still has space for two more

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.

Mgo2 is the oxidation state of manganese oxide