a. The oxygen atom (with its 2s orbital) forms a s bond with one of the three sp2 hybrid orbitals of the carbon atom; the two hydrogen atoms (with their 1s orbitals) each form a s bond with one of the three sp2 hybrid orbitals of the carbon atom.

b. The oxygen atom (with its 2p orbital) forms a p bond with one of the three sp2 hybrid orbitals of the carbon atom; the two hydrogen atoms (with their 1s orbitals) each form a s bond with one of the three sp2 hybrid orbitals of the carbon atom.

c. The oxygen atom (with its 2p orbital) forms a p bond with the pz orbital of the carbon atom; the two hydrogen atoms (with their 1s orbitals) each form a s bond with one of the two sp2 hybrid orbitals of the carbon atom.

d. The oxygen atom (with its 2p orbital) forms a s bond with one of the three sp2 hybrid orbitals of the carbon atom; the two hydrogen atoms (with their 1s orbitals) each form a s bond with one of the three sp2 hybrid orbitals of the carbon atom. The oxygen atom also forms a p bond with carbon which involves the 2pz orbitals of oxygen and carbon.