Manufacturersmay use food additives for preserving, to color, toflavor, or to fortify A B C foods. D

For preserving

First you check your [subject] and [verb] agreement and find they are ok. It is very obvious that most of the sentence is a list. Once you identify the list syntax, you realize they are infinitives, meaning option B marks the incorrect fragment. Manufacturers may use food additives to preserve, to color, to flavor, or to fortify foods.