Answer:
The correct answer is C.
Step-by-step explanation:
Edwin Hubble classified spiral galaxies according to the tightness of their spiral arms compared to the size of their nuclear bulges. This classification scheme, known as the Hubble sequence, is based on the observation that spiral galaxies can have different degrees of spiral arm tightness and different sizes of nuclear bulges. By comparing these two features, Hubble was able to divide spiral galaxies into three main categories: barred spirals, normal spirals, and flocculent spirals. The classification of a spiral galaxy into one of these categories depends on the relative size of its nuclear bulge and the tightness of its spiral arms.