Gravity , Explosion
<u>Explanation:</u>
Nebulae are made of dust and gases—mostly hydrogen and helium. The dust and gases in a nebula are very spread out, but gravity can slowly begin to pull together clumps of dust and gas. As these clumps get bigger and bigger, their gravity gets stronger and stronger.
Eventually, the clump of dust and gas gets so big that it collapses from its own gravity. The collapse causes the material at the center of the cloud to heat up-and this hot core is the beginning of a star.
Passive membrane processes are those that do not require energy and move substances down a concentration gradient; namely, these are diffusion, facilitated diffusion and osmosis.
Answer:B, D
Explanation:
When the roller coaster starts flying down the hill, it gains kinetic energy and loses potential energy.
Answer:
<em><u>is</u></em><em><u> </u></em><em><u>made</u></em><em><u> </u></em><em><u>of</u></em><em><u> </u></em><em><u>a</u></em><em><u> </u></em><em><u>double</u></em><em><u> </u></em><em><u>layer</u></em><em><u> </u></em><em><u>of</u></em><em><u> </u></em><em><u> </u></em><em><u>phospholipids</u></em>
