A serum оsmоlаlity meаsured in the emergency rоom is 326 mOsm/kg. Two hours lаter, chemistry results are: Na+ = 135 mmol/LBUN = 18 mg/dLGlucose 72 mg/dL Measured osmolality = 318 mOsm/kg Calculate the osmolal gap and indicate which of the choices given could explain the results.