That Quasars Were at Cosmological Distances Yet Appeared Like Ordinary

Multiple Choice

That quasars were at cosmological distances yet appeared like ordinary faint stars meant:

A) they were the brightest stars ever observed.
B) they must be very large.
C) they must contain many O and B type stars.
D) they must be producing such large quantities of energy than even fusion could not explaintheir output.
E) they must be very small, but bright due to gravitational lensing.