Endothelial cells are the only structure found in all parts of the circulatory system.
a. true
b. false

a. True

Explanation:

Endothelial cells

These cells are found in all the parts of the circulatory system , these are about a cell thick , and composes a wall known as the edothelium , which lines all the blood vessels , i.e. , the arterioles , veins , capillaries , arteries , venules .

Beneath the endothelial cells , there is a layer of smooth muscle cells .

of

explanation:

answer:

i don't believe the ocean is purple, but it might once have been:

as for the sky, according to nasa:

"sunlight reaches earth's atmosphere and is scattered in all directions by all the gases and particles in the air. blue light is scattered more than the other colors because it travels as shorter, smaller waves. this is why we see a blue sky most of the time."