Final answer:
Receptacles on 15- and 20-amp circuits must be of the GFCI type to ensure safety by preventing electrical shock and protecting appliances.
Step-by-step explanation:
Receptacles installed on 15- and 20-ampere-rated branch circuits shall be of the ground fault circuit interrupter (GFCI) type. This is in accordance with modern safety standards that are designed to protect individuals from electrical shock and to prevent damage to appliances due to excessive current. Circuit breakers or fuses are used to prevent thermal overload by acting as automatic switches that open when sustained current exceeds preset limits. Appliances such as toasters or refrigerators are given additional protection by having a protective case, which is part of a comprehensive approach to safety that includes the aforementioned GFCI receptacles and the three-wire system.