Oxygen and carbon dioxide are exchanged in capillaries that surround tiny sacs called bronchi.

Within the lungs, the bronchi branch into smaller bronchi and even smaller tubes called bronchioles (pronounced: BRAHN-kee-olz). Bronchioles end in tiny air sacs called alveoli, where the exchange of oxygen and carbon dioxide actually takes place. Each person has hundreds of millions of alveoli in their lungs.

Explanation:

the answer is option a.

b)

it created free trade throughout the colonial territories.