In the sentence "The suitcase was on the plane, but now it is gone," the pronouns and their antecedents are as follows:
- "The suitcase" is the antecedent for the pronoun "it."
So the correct underlined words would be:
The suitcase was on the plane, but now it is gone.
Here, suitcase is the antecedent, and it is the pronoun.