All of the following are evidence that a chemical reaction has occurred except
a. color change
b. formation of a precipitate
c. bubbles of gas
d. all of the above are evidence of a chemical reaction

answer; i believe the answer is hydraulic action;

the answer is z.

the human body has five levels of organization. level 1: cells. cells are the basic units of life and form the first level of organization. cells in the human body have specific functions. examples include nerve cells, blood cells, liver cells, and so on.