Its has to be A that's just plain common sense
Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don't require valves because pressure from the heart is so strong that blood is only able to flow in one direction.) Valves also help blood travel back to the heart against the force of gravity.
50 percent black coat colour and 50 percent brown coat colour
The simplest form of protist based on its simple cell structure and ability to change shape in response to external disturbance would be amoeba.
<h3>Amoeba</h3>
Amoeba is a unicellular organism that belongs to the division of living organisms known as protists.
Amoeba can be found in freshwater environments such as ponds, moist soils, lakes, etc. The cell contains important organelles such as the nucleus, contractile vacuole, etc.
A typical amoeba cell has no definitive shape but changes according to different environmental stimuli.
More on amoeba can be found here: brainly.com/question/2005112
