The answer is a because without them our veins would be dead
An amoeba is a single-celled animal that catches food and moves about by extending fingerlike projections of protoplasm. Amoebas are either free-living in damp environments or parasitic.
In the case of an amoeba moving, it's cytoplasm flows forward to form a pseudopodium, then it evens back out. In order to eat, it will form two pseudopodia and wrap those around to meet each other, enclosing its food, then the cytoplasm evens out again.
A substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction.
Enzymes help speed up chemical reactions in the human body.