Haemoglobin has maximum affinity for

Select INCORRECT statements with respects transport of $\mathrm{CO}_2$ by RBCs and plasma.

i. $23 \%$ of $\mathrm{CO}_2$ released from tissue cells diffuse into plasma first and then into RBCs.

ii. Within RBCs carbonic acid immediately dissociates into $\mathrm{H}^{+}$and $\mathrm{HCO}_3^{-}$.

iii. In RBCs $\mathrm{CO}_2$ combines with $\mathrm{H}_2 \mathrm{O}$ to form carbonic acid.

iv. $\mathrm{H}^{+}$ions move out of RBCs and combine with $\mathrm{Na}^{+}$to form $\mathrm{NaHCO}_3$.

v. $7 \%$ of $\mathrm{CO}_2$ is transported in dissolved form as carbonic acid in plasma.

In the light of above statements choose the correct answer from option given below.

Respiratory centres that control the rate and depth of breathing are located in __________