**Core Concept**
CO2 transport in the blood is a critical process for maintaining acid-base balance. It involves the movement of carbon dioxide from tissues to the lungs for exhalation. The main transport mechanisms include chemical buffering, transport bound to hemoglobin, and dissolved in plasma.

**Why the Correct Answer is Right**
CO2 is mainly transported bound to hemoglobin in red blood cells. This process is facilitated by the Bohr effect, where the binding of CO2 to hemoglobin is enhanced at lower pH levels. The CO2-hemoglobin complex then dissociates in the lungs, releasing CO2 for exhalation. This mechanism accounts for approximately 70% of CO2 transport.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as CO2 is not primarily transported dissolved in plasma. While a small amount of CO2 is transported in this manner, it is not the main mechanism.
**Option B:** This option is incorrect as CO2 is not mainly transported by the bicarbonate buffering system. Although this system does play a role in CO2 transport, it is not the primary mechanism.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the Bohr effect is responsible for the increased affinity of hemoglobin for CO2 at lower pH levels, facilitating CO2 transport. This mechanism is crucial for maintaining acid-base balance in the body.

**Correct Answer: C. Hemoglobin**