Which of These Techniques Has NOT Provided a Means by Which

Multiple Choice

Which of these techniques has NOT provided a means by which astronomers can infer the presence of dark matter in the universe?

A) measurement of the orbital speeds of stars near possible supermassive black holes at the centers of galaxies
B) measurement of the orbital speeds of stars in the outer regions of galaxies
C) observation of the bending of light (gravitational lensing) from remote galaxies as it passes through intervening clusters of galaxies
D) measurement of the line-of-sight speeds of individual galaxies in clusters of galaxies