Why are oxygen concentrations in the deep waters of the north atlantic higher than the concentrations found in the deep north pacific?

As explained below.

Explanation:

The North Atlantic deep water is a water mass formed deep in the Atlantic ocean and the circulation of the thermohaline layer in these ocean describes the distribution of sea salts in the ocean when the water is coo, it shrinks through the convection due to the increased density. Thus the cold water is rich in oxygen and due to the decrease in the strength f the gulf stream that brings the warm water due to the cooling experience of the North Atlantic drift. Atlantic is a growing plate and pacific is a shrinking plate. As compared to the warm and saline waters of the pacific ocean as a maximum of 37 parts per thousand is found in this ocean and being a zone of high volcanic and plate tectonic activity that brings out gases and lava at the ocean floor this area has less percentage of oxygen than Atlantic deep.

The answer is a but it also might be 7 so