(I) But-1-ene $\stackrel{\mathrm{HCl}}{\to }$ X (major) ;

(II) But-1-ene $\underset{{\left({\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CO}\right)}_2\mathrm{O}}{\overset{\mathrm{HCl}}{\to }}$ Y (major) ;

Correct statement about  X and Y is

Reaction of alkenes with HCl gives Markovnikov's product always in the presence or in the absence of hydrogen peroxide.

${\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{CH}={\mathrm{CH}}_2\underset{\mathrm{presence} \mathrm{or} \mathrm{absence} \mathrm{of} \mathrm{peroxide}}{\overset{\mathrm{HCl}}{\to }} {\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{CHCl}-{\mathrm{CH}}_3\left(\mathrm{major}\right)$