This is a unicellular protist called euglena. it lives in the water and swims around using the long flagella you see on one end. what do you, a complex multicellular human, have in common with the euglena?
a) we both can move.
b) our cells are exactly the same.
c) human cells move around using flagella.
d) the cells of multicellular organisms must be in water also.

The right answer is A.

Euglena (euglenae) is a common genus of flagellate algae, typical of Euglenophytes, and often found in water (usually freshwater, but there are rare marine species) rich in nutrients.

Men as a multicellular organism can move not through flagella but through contractions of muscle cells. In addition, there are cells inside the body such as macrophages and neutrophils that can move thanks to pseudopodia.

the fossil record provides evidence of a common ancestor to many species.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.