This is a galaxy with a characteristic pinwheel shape with a flat disk, central bulge, and graceful arms containing regions where young stars form

A spiral galaxy.

Explanation:

This is a class of galaxy described in 1936 by the American astronomer Edwin Hubble.

The central bulge is characteristic of this type of galaxies, where the major concentration of stars resides. The "arms" are very bright and are full of young, blue stars.

The pinwheel shape is why we can easily recognize them from the earth. Astronomers think that more than 60% of the galaxies in the universe are spiral-like.

d. stage 4

explanation:

the existence of some kind of demographic transition is widely accepted in the social sciences because of the well-established historical correlation linking dropping fertility to social and economic development.[1] scholars debate whether industrialization and higher incomes lead to lower population, or whether lower populations lead to industrialization and higher incomes. scholars also debate to what extent various proposed and sometimes inter-related factors such as higher per capita income,lower mortality, old-age security, and rise of demand for human capital are involved.[2]