The answer is: He is pretending to be Ernest.
In Oscar Wilde's "The Importance of Being Earnest," Algernon confronts Jack and the latter reveals that Ernest is his fictional irresponsible brother he pretends to be in order to have fun and disappear for a few days. Therefore, Algernon, who is deeply in love with Cecily, decides to show up at Jack's country state pretending to be Ernest.
The correct answer is the second option, because you don't need a comma before 'on her vacation' or before 'to Mexico', but 'Abby' needs to be separated from the rest of the sentence by commas.
What topic are you choosing?
