Physicist Dr. Lisa Kim argues that dark matter must exist because galaxies rotate faster than visible matter alone could explain.
2
readingWhich observation would best support Kim's dark matter argument?
A
Galaxies contain billions of stars
B
Outer stars in galaxies orbit at speeds that would fling them into space unless unseen mass provides gravitational pull; this mass discrepancy is consistent across galaxies
C
Space is very large
D
Telescopes have improved
Correct Answer: B
Choice B is the best answer. Speed/gravity discrepancy + consistency across galaxies supports invisible matter.
💡 Strategy: Claims about unobserved entities need indirect evidence that excludes alternatives.