Which word correctly completes the sentence: After a week, my cousin had not _____ able to think of any good slogans.

• A. was
• B. could
• C. been
• D. would

Answer: (C)

The main idea is expressing inability up to a point in the past using be able to in the past perfect. After a week, my cousin had not been able to think of any good slogans. This uses had not been able to, which shows that up to that moment in the past, thinking of slogans wasn’t possible. behalf been is needed because we’re using the perfect form of be in be able to, to talk about an ongoing state up to that past time. The other options don’t fit the grammar here: using a simple form like was would clash with the past perfect structure, and could or would doesn’t combine with had in this context to express ongoing past inability.