Suppose only one in every million stars has a solar system with a planet like Earth. How many earthlike planets would that make in the Milky Way galaxy?

I think the answer would be 1 million.

Explanation:

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

1. is geographic distribution

2 is increasing complexity

3 is transitional forms