Mystery #2Tier 2blood / oxygen
Why is blood red?
Some animals have blue blood. A horseshoe crab's blood runs pale blue, and some sea creatures have green blood. Yet slice open a strawberry-red drop of yours and it is unmistakably red, and it is red for a reason that has everything to do with the air you just breathed in. What is hiding in your blood that paints it red?
Your guess
What's your best guess about what makes blood red rather than, say, blue or green?
There's no single magic word to type, have a go in your own words, then reveal the answer to see how close you got.
Make a guess to unlock the hints and the answer.