Which protein is essential for the transport of $O_2$?

Exposure to carbon monoxide (from coal gas) is extremely dangerous and can kill a patient because

Given below are two statements:
Statement $I$: The relationship between $HbO_2$ saturation and oxygen tension $(pO_2)$ is called the oxygen-dissociation curve.
Statement $II$: The oxygen dissociation curve shifts towards the right due to a decrease in $ppCO_2$ and a decrease in temperature.
In the light of the above statements,choose the most appropriate answer from the options given below.

How much $CO_2$ is added to every $100\,ml$ of blood by the tissues (in $,ml$)?

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

Under normal physiological conditions in human beings,every $100 \ ml$ of oxygenated blood can deliver how much $O_2$ to the tissues (in $ml$)?