Option 1 -> Flaw means a defect or imperfection, not an unusual occurrence.
Option 2 -> Peculiarity means something unusual or strange, which matches "quirk" perfectly.
Option 3 -> Tradition refers to customs or practices, unrelated to the meaning here.
Option 4 -> Signal means an indication or sign, which doesn't fit the context.
Hence, Option 2: Peculiarity -> "Quirk" refers to an unusual, unexpected, or strange aspect of something. In this context, it describes the odd coincidence of both people booking the same hotel. "Peculiarity" captures this same sense of something being unusual or distinctive -> correct