What Was the Implication of the Observation by Hubble That

Multiple Choice

What was the implication of the observation by Hubble that the Cepheid variable stars he measured in the Andromeda "nebula" appeared to be very faint compared with what was expected?

A) The observed period was affected by the intense gravitational field of the "nebula" as predicted by general relativity, leading to incorrect luminosity determination.
B) The Andromeda "nebula" was very far away and was in fact a galaxy.
C) Hubble had discovered a new class of intrinsically faint Cepheid variable stars.
D) Dust and gas in the "nebula" had severely reduced the light from these stars.