The molecules in this diagram are moving in a A) random motion from one part of a membrane to another, from a higher concentration to a lower concentration. B) random motion from one part of a membrane to another, from a lower concentration to a higher concentration. C) straight line motion from one part of a membrane to another, from a higher concentration to a lower concentration. D) straight line motion from one part of a membrane to another, from a lower concentration to a higher concentration.