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1. To form a nebula, (gravity, heat, pressure) pulls matter together or causes (an explosion, pressure change, infrared light emission)

To form a nebula, pulls matter together or causes an

A nebula is a body in the heavenly bodies which contains dust and gases and they are hydrogen and helium. They are a type of galaxy in the clouds.

As a result of this, we can see that in order to form a nebula, there would have to be gravity to pull matter together which would cause an explosion because of the build up of the clumps of gas.

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Gravity , Explosion

Explanation:

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.

lizards have adapted to life in the desert. some desert lizards have toes with spiny scales to them run across the sand without sinking. some use the sand to hide from predators, or to search for small animals that they prey upon.

b. lithosphere, asthenosphere, mesosphere   is the answer most likely