Carbon dioxide is carried in the plasma asMultiple Choicecarbonic anhydrase.bicarbonate ions.carbonic acid.a gas, carbon dioxide.reduced hemoglobin.

Carbon dioxide is primarily carried in the plasma as bicarbonate ions.

Here's a step-by-step explanation:

1. When carbon dioxide (CO2) is produced as a waste product in cells, it diffuses out of the cells and into the blood, where it is picked up by red blood cells.

2. Inside the red blood cells, a small amount of CO2 binds directly to hemoglobin, but most of it reacts with water (H2O) to form carbonic acid (H2CO3). This reaction is catalyzed by the enzyme carbonic anhydrase.

3. The carbonic acid quickly dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+).

4. The bicarbonate ion diffuses out of the red blood cell and into the plasma. This is the primary way that CO2 is transported in the blood.

5. When the blood reaches the lungs, the process is reversed. The bicarbonate ion diffuses back into the red blood cell, where it is converted back into CO2 and water. The CO2 then diffuses out of the red blood cell, into the plasma, and finally out of the body when we exhale.

So, the correct answer to your multiple-choice question is "bicarbonate ions".