Answer:
B. world, has been one of the most common fish
Step-by-step explanation:
When we look at the context, we see that this sentence is meant to be the introduction of our text. It is meant to give some information about cod. "Cod," therefore, is the subject. Then, the phrase "a fish found in ocean water around the world" is an appositive. An appositive is a noun or pronoun, accompanied by modifiers, that is set next to another noun in order to modify it. Finally, in order for the rest of the sentence to make sense, we need a verb, which in this case is "has been."