was/has been used in the previous sentence

[EngLearner]

Suppose I'm analyzing the following sentence: "Yesterday, I saw a cat. The cat was stalking a bird." I say the following:

The definite article "the" is used before the word "cat" because the combination of that word with the indefinite article "a" — "a cat" — was/has been used in the previous sentence: the first sentence introduces "a cat," which is indefinite, meaning it's not referring to a specific cat; in the second sentence, "the cat" is used because it refers to the same cat mentioned earlier, now known to the reader.

Is either tense appropriate here?

 

[jutfrank]

If you're going to use 'is used' in the first part of the sentence, then why not use 'is used' again?

The definite article "the" is used before the word "cat" because the combination of that word with the indefinite article "a" — "a cat" — is used in the previous sentence:

The present simple is perfectly appropriate in both places here. Using the present perfect in the second position is also a good choice as it casts a retrospective aspect—you're looking back at the first sentence from the perspective of the second.