Answer:
B. Transport of molecules across a membrane from a high to low concentration gradient by means of a carrier protein
Step-by-step explanation:
According to this diagram showing the presence of certain molecules on one side of the membrane, making their way to the other side across the membrane. Due to the difference in concentration on either side of the membrane, a concentration gradient is formed.
Based on the diagram, the movement or transport of molecules is occurring from a region of high concentration to a region of low concentration. This means that it's a form of PASSIVE TRANSPORT, however, the molecules are being transported across via the aid of CARRIER PROTEINS as depicted in the image.