What is the definition of gravity in simple terms?

Gravity, also called gravitation, in mechanics, the universal force of attraction acting between all matter. ... On Earth all bodies have a weight, or downward force of gravity, proportional to their mass, which Earth's mass exerts on them. Gravity is measured by the acceleration that it gives to freely falling objects

1 : A force of attraction that tends to draw particles or bodies together.

2 : The attraction of bodies by the force of gravity toward the center of the earth.

3 : Great seriousness.

i wanna say it’s between b and d, leaning more towards b.

c)as speed changes, wavelength and frequency change.

everything changes!