The inner planets are usually rocky because the gravitational pull is stronger closer to the star or in this case the sun. The dust and rocky particles that are left over after a super nova or in a nebula will tend to orbit closer to a proto-star when a solar system is in its early days. In our solar system these planets are Mercury, Venus, Earth and Mars. Gases are less dense and will be less affected by the pull of gravity because rocky particles have more mass. The outer planets are gas giants formed from clouds of gas that would be further out in the spinning disk around a proto-star.
Like a lot of other things, (gravity, sound, electrostatic force), brightness also decreases as the square of the distance.
When the source moves to a new position that's 4 times as far away, its apparent brightness becomes (1/4^2) its original value.
That's 1/16 .
I can't see the answers clearly, but I can see the question. So, I'll just give you a clue/hint.
A stars brightness actually depends on how far it is from your location. If it's far away, it will be dimmer than its counterpart that is closer. To summarize it, if two stars have the same brightness level and one is farther away than the other, the one farther away will appear dimmer than its closer counterpart.
