The atom? gas? either one of those two would work
Epiglottis
The epiglottis is a flap of cartilage the covers the entrance to the throat protecting the lungs from obstruction. It moves when we swallow to allow food in.
The tricuspid valve, located between the right atrium and the right ventricle; the pulmonary (pulmonic) valve, between the right ventricle and the pulmonary artery; the mitral valve, between the left atrium and left ventricle; and. the aortic valve, between the left ventricle and the aorta.
There is external and internal so I'll list th external. The most important is skin then mucus, sweat or secretion, hair, nails and tears which are all part of the integumentary. Some internal defenses are white blood cells and T cells.
Answer:
2, phenotype
traits are determined using genetics
