Among the following, which hydrolysis reaction occurs at the slowest rate?

Vinyl chloride (${\text{CH}}_2\text{=CH-Cl}$) undergoes nucleophilic substitution at the slowest rate. This is because the lone pair on the chlorine atom is in resonance with the $\pi$ -bond of the double bond. This gives the $\text{C-Cl}$ bond partial double bond character, making it very difficult to break compared to pure single bonds in alkyl or benzyl halides.