Final answer:
The word 'guise' in the given sentence means 'costume'. A guise is an external presentation often used for pretense, as seen in various activities such as cosplay and Renaissance Faires where people wear distinctive costumes to imitate different characters or historical figures.
Step-by-step explanation:
In the sentence 'Robin adopted the guise of a mummy on Halloween,' the word 'guise' refers to option 1) costume. This term means the external appearance, style of dress, or a way of presenting oneself that is typically different from one's true nature or character, often used to deceive or pretend. In this context, Robin is dressing up as a mummy, which is a common Halloween costume. A costume can be seen as a form of disguise or guise, and people often use costumes to transform into characters or identities different from their own.
Cosplayers, Renaissance Faire attendees, and reenactors at living history museums are examples of individuals engaging in the act of donning costumes. Whether to celebrate historical accuracy, participate in role-playing activities, or simply have fun, the use of costumes allows people to temporarily adopt an alternate identity.