How does the boiling process at supercritical pressures differ from the boiling process at subcritical pressures?

Super critical, the fluid won't bubble. As you warm it, It will gradually change its properties to be an ever increasing number of gas like until the point when it winds up unclear from a gas. There is no stage change over the critical point. Though at subcritical pressures, there is dependably an distinct surface between the phases.

They carry out the exchange of gases as we breathe ( oxygen and carbon dioxide).

The answer is c) pyrite