1. I don't really enjoy ____ (travel) by plane.
travelling to travelling to travel

2. I noticed the two men in front of me ____ (smoke).
to smoke smoking smokes

3. They blew smoke at me instead of ____ (apologize).
apologizing apologized to apologize

4. I couldn't believe they kept on ____ (do) that.
done to do doing

5. Then, they began ____ (argue) with me.
argued arguing argueing

6. The other passengers started ____ (look) at us.
look looked to look