Answer: Ammonia (NH3)
Explanation: The other choices include: Vinegar which is Acetic Acid; HCl or Hydrochloric Acid; and HNO3 or Nitric Acid, so by a process of elimination, Ammonia is the only likely answer. A more thorough explanation: ammonia abides by the Brønsted–Lowry definition of a base: wherein it is any compound that can accept a proton from another molecule. It just so happens that, given Ammonia (NH3) in water, Ammonia will accept a proton in the form of H+ from water and form Ammonium (NH4) and Hydroxide ions (OH).