Haemoglobin is

Name the enzymes $A$ and $B$ in the following equation:
$CO _2+ H _2 O \underset{B}{\stackrel{A}{\rightleftharpoons}} H _2 CO _3 \underset{B}{\stackrel{A}{\rightleftharpoons}} HCO _3^{-}+ H ^{+}$

Which enzyme is present in $RBC$s and plasma to catalyse the given reaction: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$?

Identify the correct statement with reference to transport of respiratory gases by blood?

What is true about $RBCs$ in humans?

Select the correct option:
$(1)$ Approximately $97\%$ of $O_2$ is transported by plasma / RBCs.
$(2)$ The primary site of gas exchange is alveoli / bronchioles.