In the 1960s, Maarten Schmidt Determined That Quasars Were Very

In the 1960s, Maarten Schmidt determined that quasars were very distant objects by

A) determining how luminous they were.
B) determining how small the source of light was from its luminosity variations.
C) discovering that they were embedded in distant galaxies.
D) determining their redshifts.
E) determining their parallax angles.