Fish has become expensive

[Rachel Adams]

This example is from "English Grammar in Context" by Michael Vince. Should it be "has become" because at the end of the sentence they use "it"? But why "has become" and not "have become" if fish is referred in a general way?
I uploaded the screenshot of the exercise.


"In recent years, fish in the UK (become) expensive and many people have stopped eating it."

 

[SoothingDave]

Yes, "has become" is correct. It's referring to the type of meat, not to the animals.