Answer:
Lemon
Explanation:
The process in which the exposed "interior" of an apple becomes/turns brown is caused by enzymatic actions in the apple. This browning reaction occurs in many fruits and tubers (like banana and yam). This process requires oxygen to proceed and hence can be restricted by the presence of an antioxidant. Ascorbic acid is an antioxidant that can assist in countering the effect of the oxygen molecules in this browning.
Lemon contains a good amount of ascorbic acid which can assist in counteracting the effect of oxygen and prevent the browning from taking place.
