The human respiratory system.

trachea, bronchi

trachea, bronchi, lungs

trachea, bronchi, lungs, diaphragm and the muscles between the ribs.

trachea, bronchi, lungs and ribs.

the diffusion of gases into and out of the body.

the difussion of gases into the body.

the diffusion of gases out of the body.

the diffusion in the lungs.

tiny, air-filled space inside the lungs.

respiration that uses oxygen.

a blood vessel.

the diffusion of gases.

a kind of fiber.

a kind of cabohydrate.

a kind of sugar, used as energy source by living things.

a kind of energy used by living things.

respiration that uses gas.

respiration that uses carbon dioxide.

respiration that provides oxygen.

respiration that uses oxygen.

that you can swim.

that you can do exercises.

that you do not smoke.

that you do moderate exercises easily, without tiring too quickly.

is a disease.

is a drug .

is a cigarette smoke.

is a substance.

HIV

AIDS

Smoking

Cancer

a visible gas.

tiny particles of soot.

a substance.

an invisible gas.

tiny particlesof soot.

are big particles of soot.

are tiny substances.

are tiny particles of soot and other substances.

it is difficult to stop taking it.

it is easy to stop taking it.

it is impossible to stop taking it.

it is possible to stop taking it.

the amount of carbon dioxide.

the amount of oxygen.

the amount of oxygen transported in the blood.

the amount of oxygen transported in the veins.