This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
CO2 is mainly transported in the blood in which form: 
Select and explain. 
A. Dissolved form, B. HCO3, C. Carbamino compound, D. Gas form
B: HCO3
Answer: B: HCO3 
Explanation: CO2 is transported in the blood in 3 forms:

As HCO3- CO2 is mainly transported in bicarbonate form - 70%. When CO2 diffuses into RBC, it reacts chemically with water and with help of enzyme carbonic anhydrase it is converted into HCO3 + H + CO2+ H2O → HCO3+H +​
As dissolved CO2: 6 - 7% of CO2 transport​
As carbamino compound of Hb and other plasma proteins: 20% of C02 transport.