Hey Haewon! =)
Sure, I can check your reasoning!
To your points:
1. Yes! The "cooling" system is a great context clue.
2. Yes! Car focuses on the colors
3. Yes! Absolutely... color of animal --> relates to a cooling system. Black doesn't make sense as a color to keep cool (since black absorbs heat and makes things hotter, right?). You aren't really inferring too much; instead, you are "connecting the dots." =) Since "thermoregulation" (regulating heat) in (B) most closely matches the focus of the essay, that is the answer you want to go with.
Good job with your reasoning!
Keep it up! You got this, Haewon!