What is true about RBCs in humans?

A. They carry about 20-25 per cent of $$C{O_2}$$  

B. They transport 99.5 per cent of $${O_2}$$

C. They transport about 80 per cent oxygen only and the rest 20 per cent of it is transported in dissolved state in blood plasma

D. They do not carry $$C{O_2}$$ at all