The correct option is B Tert-butyl bromide
Relative rates of 1o and 3o H atoms by bromine are 1:1600.
Tert butyl bromide is formed by displacement of 3o H. It is only one in number. Its relative rate of displacement by bromine is 1600.
Formation of 1-bromo-2-methyl propane (Isobutyl bromide) takes place by replacemnt of any of the nine 1o H atoms. But relative rate of displacement of 1o H is 1. Total relative rate of displacement of all the nine 1o H atoms is 9.
% of tert butyl bromide = 16001609×100= >90%
% of iso butyl bromide = 91609×100= <10%
So, major product is tert-butyl bromide.