Question

1.

In humans, oxygen enters the bloodstream from the
. (1) diaphragm
(3) trachea
(2) air sacs
(4) nasal cavity

Answer 1

Oxygen enters the blood stream through the alveoli, which are tiny air sacs in the lungs where gas change is exchanged. Carbon Dioxide goes in through the alveoli and out goes oxygen.

2. air sacs

Hope this helps ;)