Question

An unlabeled hierarchical diagram of various astronomical bodies is shown below. The labels A, B, C, and D can be used to represent the Milky Way, Earth, universe, sun, and solar system.
An image of four circles nestled one within the other is shown. The lower boundary of all four circles touch one another. The largest and the outermost circle is labeled A. The next circle in order is labeled B. The next circle is labeled C. The innermost circle is labeled D.

Part 1: Which four astronomical bodies would you choose to represent the four labels in the diagram?
Part 2: Which astronomical body, other than the ones given, could also represent the label D?

Answer 1

A) The biggest astronomical object is the Universe, which contains billions of galaxies among which there is the Milky Way.
The Milky Way contains thousands of planetary systems, among which the Solar System.
The Solar System contains many planets (but only one star, the Sun), among which there is Earth.
Therefore you can label:
A = Universe, B = Milky Way, C = Solar system, D = Earth

b) Given what we said before, you could label D also any other planet in the Solar System, therefore you can choose among Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune.