Which of the following is most stable?

 The major product is:

The bond dissociation energy at the $\mathrm{C}-\mathrm{H}$ bond for the compound:

$\left(\mathrm{I}\right)$ ${\mathrm{CH}}_3\mathrm{H}$

$\left(\mathrm{II}\right)$ ${\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{H}$

$\left(\mathrm{III}\right)$ ${\mathrm{CH}}_2=\mathrm{CH}-{\mathrm{CH}}_2-\mathrm{H}$

$\left(\mathrm{IV}\right)$ ${\mathrm{C}}_6{\mathrm{H}}_5-\mathrm{H}$