Could or was/were able to (см. вложение)

1. so we could have a picnic 2. but he was able to finish his speech 3. could understand the language 4. I was able to catch the 9.55 a.m. train 5. he was able to solve 6. we could find 7. he was able to work 8. he was able to ski 9. I was able to see 10. I couldn't hear 11. we were able to continue 12. fortunately I could wake my sister