ph-CH=CH-$\stackrel{\mathrm{O}}{\stackrel{\parallel }{\mathrm{C}}}$-OH 

The IUPAC name is:

(a) 3-phenyl prop-2-enoic acid

(b) 3-phenol prop-1-enoic acid

(c) 3-carboxy-prop-1-ene benzene

(d) but-2-enoic acid