How much oxygen is delivered to the body tissues by blood during one circulation (in $\%$)?

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

What are $P$ and $Q$ in the given reaction?
$CO _2+ H _2 O \underset{Q}{\stackrel{P}{\rightleftharpoons}} H _2 CO _3 \underset{Q}{\stackrel{P}{\rightleftharpoons}} HCO _3^{-}+ H ^{+}$

Approximately $97\%$ of $O_2$ is transported by $RBCs$. The remaining $3\%$ is transported by:

The toxic effect of carbon monoxide is due to its greater affinity for haemoglobin as compared to oxygen by (approx.) (in $\times$)

Explain the oxygen dissociation curve. Explain the factors required for the transport of $O_2$ by it.