Which event would most likely occur if earth did not retain the heat from its formation? a-the inner core would liquefy. b-seismic waves would move the crust. c-the earth’s magnetic field would disappear. d-the asthenosphere and outer core would solidify.

I believe it's D don't take my word for it.

Option (D)

Explanation:

The earth's core is extremely hot due to which the outer core is liquid in nature and it plays the most significant role in the plate tectonic movement, where the convection cells are formed in the mantle that drives the plates to move over the less dense layer of the asthenosphere.

The scenario would have completely changed if there were no heat energy trapped in the core of the earth. In absence of this heat source, the rocks that are present in both the outer core and asthenosphere would have been entirely solid in nature. The convection current also would have not formed in the mantle and the plates would have remained stationary.

Thus, the correct answer is option (D).

sound moves fastest in solids because the molecules are tightly packed and it allows sound to vibrate

yes, because even though a theory has a  lot of evidence to support it, it is not always true