I'm currently studying for an organic chemistry exam and I came across polar protic solvents. I read that polar protic solvents have active hydrogen atoms that are involved in hydrogen bonding and that compounds with functional groups -OH, -NH2, -CO2H, and -SH are usually protic solvents. Then I went over a concept check question which asked whether H2O or H2S was a better protic solvent. The answer was that H2O was because it will form hydrogen bonds with the solute then it went on to say that only hydrogen atoms bonded to O, N, or F form hydrogen bonds with other atoms, thus what has confused me. If protic solvents are involved in hydrogen bonding and compounds with aforementioned functional groups are protic solvents then if the above statement is true how can compounds with the thiol and carboxylic acid functional groups be considered protic solvents?