An apple browns where it is cut because the knife breaks op cells th had ke two subst apart. A enzyme sto in o part o the ce is sudd free to act on a substance held in another, and the reaction with oxygen in the air produces a dark pigment within minutes. Lemon juice slows the change because acid disables the enzyme, and cold water works by keeping oxygen away from the surface. Neither trick repairs the damage; both simply interrupt a process already under way.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.