Among the following, more polar is

The polarities of the molecules depend on the difference in the electro negativities of bonding atoms. If E.N of bonded atoms is high then the molecule is more polar.

The decreasing order of the E.N of halogen atoms is F > Cl > Br > I . The decreasing order of polarity of molecules is given in the below.

HF > HCl > HBr > HI

Therefore, among the given all HF is the most polar.