Bleach boils at 101°C. Isopropyl alcohol (rubbing alcohol) boils at 82.5°C. Vinegar boils at 100.6°C. Water boils at 100°C. A student has an unknown clear liquid. She wants to determine what it is, so she decides to boil the liquid and use the boiling point as a means of identification. The liquid starts boiling at 99°C. Based on the boiling points shown, which substance is it?