The document is a grammar challenge that tests the ability to choose between the past perfect and present perfect tenses. It provides a sentence with blanks to fill in using "had been", "has been", or "had seen" depending on which tense is correct. The correct answers are "had been" and "had seen" as they refer to an action that was completed in the past.

1. Challenge:
• Guess and choose: Past Perfect or Present Perfect
Answer:
Kristine_____ never_______ to an opera before last night;
she __________ it twenty times since yesterday.
Had – Been/ Has Seen
Has Been/ Had seen