HELP look at THE PICTURESSS I WILL GIVE YOU POINTS AND BRAINLIEST ANSWERS IF YOU KNOW DON"T ANSWER IF YOU DON'T KNOW JUST FOR THE POINTS and take your time to think take as much time you need plzz help

A__ is two or more substances that are together in the same place but are not chemically combined

How are isotopes of the same chemical element alike? how are they different?

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.