Final answer:
The gravitational lens effect observed for quasars underscores the presence of dark matter (C), confirming theories about the distribution of dark matter and supporting the notion of supermassive black holes at the center of quasars.
Step-by-step explanation:
The discovery of the gravitational lens effect for quasars suggested the presence of dark matter (C). The gravitational lens effect, as described by Albert Einstein's theory of general relativity, occurs when massive objects, including visible galaxies and dark matter, bend the fabric of spacetime and consequently the path of light passing near them. This effect has allowed astronomers to observe lensed images of distant galaxies and calculate detailed maps indicating the distribution and amount of dark matter within galaxy clusters.
Despite having significant implications for our understanding of supermassive black holes, which power quasars, and confirming their small size, the association with dark matter is more direct when considering the lensing effect. Observations of these lensing effects have shown that galaxy clusters contain far more dark matter than luminous matter, and these studies have been instrumental in increasing our knowledge of dark matter's existence and properties.