MISSING LINK CXLVII

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. School..........Sketch..........Scrap
2. Light..........Middle..........Heavy
3. Dog..........Turtle..........Eagle
4. Bird..........Hare..........Lame
5. None..........Code..........Bell
6. Pepper..........Flour..........Paper
7. String..........Score..........Tongue
8. Pencil..........Paint..........Monkey
9. Key..........Surgery..........Scale
10. Animal.......Vegetable.......Mineral

Answers:

1. Kinds of books
2. Weight
3. Sea
4. Brain
5. Bar
6. Kinds of mills
7. Things that can be tied
8. Grease
9. Things that can be major or minor
10. Classic categories for "Twenty Questions"