Which branched chain isomer of the hydrocarbon with molecular mass 72u gives only one isomer of mono substituted alkyl halide?

The reagent is neopentane which undergoes mono chlorination to give Neopentyl chloride as product which is a mono substituted alkyl halide.

 Neopentane gives only one isomer of the mono substituted alkyl halide. Neopentane, also known as 2,2-dimethylpropane, is a five-carbon-atom double-branched alkane.