Correct Answer - A
More stable the free radical formed upon homolytic fission of C-H bond, lesser is the bond dissociation energy. Since the stability of the radicals formed from toluene, benzene, n-pentane, 2, 2-dimethylpropane follows the order :
`C_(6)H_(5)overset(*)(C)H_(2) gt (CH_(3))_(3)overset(*)(C) gt CH_(3)overset(*)(C)HCH_(2)CH_(2)CH_(3) gt overset(*)(C_(6))H_(5)`, therefore, the C-H bond of toluene has the lowest bond dissociation energy.
