Many buffalo in North America were killed because of human thoughtlessness. As a result, there are few buffalo left in North America. People (not, kill) _______ those buffalo.

A: Have you seen Clark? I can’t find him anywhere. – B: He was feeling terrible. He _______ (go) home a while ago.

We did not travel to Africa when we had the opportunity last year. We (go) ______ at that time.

Sally gave a speech at her graduation. I think I saw tears in her parents’ eyes. – Oh, that is touching. They ____ (be) very proud of her.

We painted our house. Now it’s white and has beige shutters. It doesn’t look good. We (not, paint) _______ our house in such dull colors.

Scientists are not sure why the Mayan civilization collapsed. The Mayans (have) _____ enough to eat, or perhaps their enemies became too strong for them.

Bob: Hey, you guys! You are not supposed to ride your bikes on the sidewalk! You could crash into someone! Sue: They (hear) ______ you, Bob. Look! They just kept going.

How were you able to stay awake during that long, boring lecture?- It was difficult.

Jim: Look! There are lights on in hte Thompson’s house. Didn’t they go away on vacation? Ann: They (leave) _______ yet. Or maybe they left the automatic timer on to deter burglars.

A: You’ve been on the go all day. Aren’t you exhausted? B: Yes, I _____. I can’t remember when I’ve ever been this worn out.