Exercise 71.1: Ago or before

Fill in the blank with ago or before.

Example: It's six o'clock. The office closed half an hour ____.
Answer: It's six o'clock. The office closed half an hour ago.

1. I have seen that error ____.

2. Maria began typing that letter ten minutes ____.

3. Can you believe people didn't have computers 20 years ____.

4. Have you thought about that ____.

5. I just thought about it a few minutes ____.

Unit 71