A volcano is a that opens downward to a pool of molten rock below the surface of the earth

b. the carbon cycle ensures living things have a source of hydrogen

the supermassive black hole is in the middle of the galaxy.

he movement of air through earth's or any planet's atmosphere is called wind, and the main cause of earth's winds is uneven heating by the sun. this uneven heating causes changes of atmospheric pressure, and winds blow from regions with high pressure to those with low pressure.

i hope this : )