D) It was his usual custom to wash his hands before each meal.
When one is redundant, one basically says the same thing twice or says something that is unnecessary. For instance, it would be redundant to say “wet water” because water, by its nature is wet. Thus, when we look at Option D, the redundancy it contains is “usual custom.” This is redundant because an act that is customary, or is a custom, is so because of its usual practice.
