For these reasons blood is an example of which type of mixture

heterogeneous

Explanation:

it's a heterogeneous mixture called a colloid.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

this is math not biology xd