Out of the given options, option 1, BF3, option 2, AlCl3, and option 4, C6H5OH, are all considered acids. However, option 3, NH3, is not an acid.

Option 1, BF3, is boron trifluoride, which is a Lewis acid. It accepts a pair of electrons during chemical reactions.

Option 2, AlCl3, is aluminum chloride, which is a Lewis acid as well. It can accept a pair of electrons from other compounds.

Option 4, C6H5OH, is phenol, which has acidic properties due to the presence of a hydroxyl group (OH). It donates a proton during chemical reactions.

On the other hand, option 3, NH3, is ammonia. It is a base rather than an acid. NH3 can accept a proton (H+) from an acid to form NH4+.

Overall, all the options listed except for option 3, NH3, can be considered acids.