I hate sitting ...... him as he always smells of garlic.

Solution (By Examveda Team)

I hate sitting beside him as he always smells of garlic.
In this context, "beside" is the correct preposition to use, indicating the physical proximity or position next to someone. Therefore, "beside" is the most appropriate choice to complete the sentence, accurately conveying the speaker's dislike for sitting next to someone who smells of garlic.