I need help ASAP Which pair of elements is most likely to form an ionic compound with each other? Thank you A) potassium, calcium
B) oxygen, nitrogen
C) sulfur, oxygen
D) calcium, chlorine
E) iron, potassium

If a solution had a ph of 7 what is the solution

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.

Mary is conducting an experiment on how pollution affects plant growth. how can she ensure that her data are reliable?