Jim is in a crowd of people at the mall looking for his girlfriend Tammy, who was supposed to meet him for dinner. Jim realizes Tammy is across the room as he catches a whiff of her overpowering perfume. Which process explains why Jim is able to smell the perfume?

A. osmosis

B. diffusion

C. active transport

D. facilitated diffusion

The answer would most likely be B, diffusion. Diffusion is the process of molecules going from an area of higher concentration of those particles (around Tammy) to an area of lower concentration (around Jim who is across the room), without the use of energy, as they are going with the concentration gradient (higher concentration to lower concentration). In this question, the molecules would be the molecules of Tammy's perfume. The area around her has a higher concentration of perfume particles, as she sprayed the perfume on herself. The area around Jim would be the area of lower concentration, as there are less molecules of perfume around him. Osmosis is the diffusion of water molecules from an area of higher water concentration to an area with a lower water concentration through a semi-permeable membrane. Active transport is the process of diffusion, however, it requires energy as the molecules go across their concentration gradient (from low concentration to high concentration). Facilitated diffusion is the process by which molecules go from a higher concentration to a lower concentration. However, the molecules go through a cell's membrane with the aid of proteins on the membrane. Therefore the answer would be diffusion.