The Discovery of the Expanding Universe Began in 1914 When

Multiple Choice

The discovery of the expanding universe began in 1914 when V. M. Slipher realized that 11 of the 15 spiral "nebulae" he imaged showed redshifts. Why only 11?

A) His measuring instruments were not fine enough to show the redshifts in the others.
B) He included nearby open clusters in his sample.
C) By chance he included in his sample active galaxies with jets. The redshifts of the galaxies were masked by the blueshifts of the jets.
D) He was looking at nearby galaxies in the Local Group, and many of these have intrinsic velocities that are larger than their participation in the Hubble flow.