The correct option is C (CH3)3∙C<(CH3)2∙CH(C6H5)2∙CH<(C6H5)3∙C
The correct order of stability of free radicals is:
(CH3)2∙CH<(CH3)3∙C<(C6H5)2∙CH<(C6H5)3∙C
More the number of phenyl ring, more the number of resonating structure and hence more is the stability.
Similarly, more the number of αH, more will be the hyperconjugative structure and hence stability will be more.