The structure of propenoic acid is shown here. indicate the type of hybridization for each numbered atom.

In Chemistry, hybridization is referred as steric number which is all about the regions of electron density that surrounds an atom. In this given problem, the structure of propenoic acid, here is the type of hybridization for each numbered atom:

Label 1, 2, 3 and 5 are all sp2

Label 4 is sp