Final answer:
Viola dressing like a boy is an example of situational irony in 'Twelfth Night' by William Shakespeare.
Step-by-step explanation:
Situational irony is when the outcome of a situation is different from what was expected. Out of the given options, an example of situational irony is 1) Viola dressing like a boy. In the play 'Twelfth Night' by William Shakespeare, Viola disguises herself as a young man named Cesario to navigate the society. This leads to various comedic and ironic situations.