Which of the following sentences best describes osmosis? A. The cell uses energy to pump molecules across the membrane.
B. Water molecules flow from high to low concentration.
C. Water molecules flow from low to high concentration.
D. No cellular energy is required to move glucose molecules across the membrane​

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.