The correct option is C III
This reaction is Friedel-Crafts Alkylation reaction which is an example of electrophilic substitution reaction.
The groups which direct the incoming group to ortho and para positions are called as ortho and para directing groups. Electron density is more on ortho and para position. Therefore, substitution takes place mainly on ortho and para positions.
-OMe is ortho-para directing group. Further due to large size of t-butyl group, para-substitution predominates to give less hindered structure. Hence, the correct answer is option (c).