Question

Veins can be differentiated from arteries because the veins:
Have valves
Have hard walls
Have pure blood in them
Have thick walls​

Answer 1

Have valves

Explanation:

Arteries carry oxygenated blood from the heart to other body parts of the body, thus the movement of the blood is towards the gravity.

Veins carry deoxygenated blood from all parts of the body back to the heart. This flow in veins is against the gravity since the blood from the appendages is to be carried to the heart.

Thus to prevent the back flow of this blood veins have valves to prevent the reverse movement.