Which formula represents hydrofluoric acid?

Hydrofluoric acid is represented by the formula HF, which consists of one hydrogen atom bonded to one fluorine atom. In this compound, the hydrogen is the acidic part, and the fluorine contributes to the properties of the acid due to its high electronegativity and ability to form strong hydrogen bonds.

The other formulas do not accurately represent hydrofluoric acid. H2F2 suggests that there are two hydrogen atoms for every two fluorine atoms, which does not reflect the composition of hydrofluoric acid. HF3 shows three fluorine atoms, which is not correct since hydrofluoric acid has only one fluorine. Finally, F2H indicates a different arrangement where there are two fluorine atoms bonded to one hydrogen atom, which does not correspond to the structure of hydrofluoric acid either. Thus, HF is the only correct representation among the choices given.