Tertiary alkyl halide among the following is

• Tertiary alkyl halides are those in which a halogen atom is joined to a tertiary carbon atom (i.e. a carbon atom attached to three other carbon atoms). 
• Chlorine is attached to a tertiary carbon atom in making it a tertiary alkyl halide.${\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{C}\left({\mathrm{CH}}_3\right)\left(\mathrm{Cl}\right)-{\mathrm{CH}}_2-{\mathrm{CH}}_3$, 

Hence, the correct answer is option (D)  3-Chloro-3-methyl pentane.