What is true about $\text{RBCs}$ in humans?

1. A
   They do not carry ${\text{CO}}_2$ at all.
2. B
   They carry about $20-25\text{ percent of }{\text{CO}}_2$.
3. C
   They transport $99.5\text{ percent of }{\text{O}}_2$.
4. D
   They transport about $80\text{ percent oxygen only}$ and the rest $20\text{ percent}$ is in dissolved state.