Living things contain units of structure and function that arise from preexisting units. This statement best describes the A) cell theory
B) lock-and-key model of enzyme activity C) concept of natural selection
D) heterotroph hypothesis

cell theory

Explanation:

cells are the basic unit of structure in organism

its like this, "if i give a plant an unlimited amount of sunlight,then the plant will grow to its largest possible size."

hope it let me know if it does or doesn't =^-^=