MISSING LINK CXX

Each trio of words below shares a Missing Link - that is, its members have something in common, obvious or not. For example, RIVERS, NOSES, & VIOLINS can all have BRIDGES.

1. Level..........Sight..........Opener
2. Iron..........Journey..........Tin
3. Air..........Pin..........Jar
4. Wagon..........Bullet..........Gravy
5. Seat..........Temper..........Potato
6. Back..........Bill..........Buck
7. Cold..........Ice..........Vacuum
8. Bird..........Bath..........Bunk
9. Office..........Floor..........Personal
10. Density..........Definition..........Energy

Answers:

1. Eye
2. Man
3. Kinds of heads
4. Kinds of trains
5. Things that can be hot
6. Board
7. Pack
8. Kinds of houses
9. Space
10 Things that may be high