According to the statement, his movements are affected but only a little bit, hence the correct answer would be option B, as “slightly” means only by a little amount, hence it is correct because that means that movements are only slightly affected, and he is still active.
Option A is incorrect because “entirely” means “fully” or completely, which is incorrect because according to the statement, he is still very active, hence the movements are only slightly affected.
Option C is incorrect because “nowhere” means not in or to any place, not anywhere, which is incorrect here because level of movements are being spoken about.
Option D is incorrect because “frequently” means very often, which is incorrect here, because “his movements are frequently restricted” means that he can hardly make any movements which is incorrect as is he is still very active.