Which of the following compounds possesses the $C-H$ bond with the lowest bond dissocation energy :

$(a)\;Toluene \\ (b)\;Benzene \\(c)\; n-pentane \\ (d)\;2,2-Dimethyl propane$

C-H bond dissociation energy is the lowest where free radical produced is the most stable.
Out of all these free radicala, benzyl free radical is the most stable since it is stabilized by resonance .
Thus, toluene has the lowest C-H bond dissociation energy .
Hence a is the correct answer.