What is true about RBCs in humans?

They carry about 20-25 percent of \( \mathrm{CO}_{2} \).

They transport \( 99.5 \) percent of \( \mathrm{O}_{2} \).

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

They do not carry \( \mathrm{CO}_{2} \) at all.