Why are stars drawn as different sizes on a sky atlas, like as shown with Orion?

When you look in a sky atlas, you might see diagrams like this: ... This type of schematic draws the stars as different sizes to represent different brightnesses. ... In almost every star atlas, you will see Orion drawn with these same lines. ... Barnard's Loop is a cloud of faintly glowing gas, which can't be seen without a telescope ...

Explanation:

the correct answer is c.

the correct answer is c