How is $70\%$ of carbon dioxide transported by the blood to the lungs?

Although much carbon dioxide is carried in blood,yet blood does not become acidic because

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

$A$: $100 \; ml$ of venous blood contains $14.4 \; ml$ of $O_2$,meaning it is still $75\%$ saturated with oxygen under normal conditions.
$R$: About $4.6 \; ml$ of $O_2$,i.e.,$25\%$,diffuses from arterial blood into the tissues during resting conditions.

The process of migration of chloride ions from plasma to $R.B.C.$ and bicarbonate ions from $R.B.C.$ to plasma is known as:

Hamburger phenomenon is also known as