What is the primary form in which oxygen is carried in blood? as carbonic acid in plasma chemically bound to hemoglobin dissolved in plasma as a bicarbonate ion in plasma?

The correct answer is chemically bound to hemoglobin.

In the blood, oxygen is combined with hemoglobin, that is, a protein found in the red blood cells. Hemoglobin refers to a protein that can combine with four molecules of oxygen.

Oxygen is not carried in the plasma; it is carried by the red blood cells. These cells comprise of a red element known as hemoglobin that combines with oxygen and transports it around the body in the blood and then lets it go when required.