Question

What is thought to be most responsible for the salinity of the oceans?

Earthquakes stirring up the ocean floor.
Chlorine gas combined with sodium from Earth's rocks.
Volcanoes releasing gas
Natural run-off from mountain ranges.

Answer 1

I would say B, because as temperature cools, the gas descends and gets in contact withthe solid. Plus, chlorine reacts spontaneously with Sodium, the reaction why in a short amount of time, significant number of reaction have taken place and the formation of NaCl, is a salt. Increasing the ocean's salinity.

Answer 2

As for B and C where gases are given off, cannot be correct, becaue gases ascend rather than descend, hence they would not react with sodium anyway, which is at the bottom.