Riddle

I am needed for most animals and hardcover books. What am I?

Choose an answer

A.A cover
B.A frame
C.A skeleton
D.Spine
Hint: It's a word with 5 letters, starting with "S".

Answer

Spine

Why this is the answer

Vertebrate animals need a spine (backbone) for support, and hardcover books have a spine that holds the pages together.

This riddle is filed under "What Am I?" Riddles and rated Medium.