Which discovery by astronomer Vera Rubin helped prove the existence of dark matter? HELP MEEEH :c

Galaxies exist outside of the Milky Way.
The expansion of the universe is accelerating.
Galaxies spin faster than they should, based on their visible matter.
Gas giants form farther from the Sun, where temperatures are cooler.

Match the scale and the actual area to the area of the corresponding scale drawing. scale: 1 inch to 4 feet actual area: 128 square feet scale: 1 inch to 7 feet actual area: 147 square feet scale: 1 inch to 8 feet actual area: 256 square feet scale: 1 inch to 5 feet actual area: 225 square feet area of scale drawing scale and actual area scale drawing area: 3 square inches arrowright scale drawing area: 8 square inches arrowright scale drawing area: 4 square inches arrowright scale drawing area: 9 square inches arrowright