The winter solstice occurs at the
of the earth's orbit, meaning.
the sun

correct answer is a. and d.

trachea, alveoli, lung capillaries, arteries

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%