Riddle

I build up castles. I tear down mountains. I make some men blind, I help others to see. What am I?

Choose an answer

A.Wind
B.Water
C.Fire
D.Sand
Hint: It's a word with 4 letters, starting with "S".

Answer

Sand

Why this is the answer

Sand can be built into sandcastles, wind-driven sand erodes mountains over time, sand can blind in a sandstorm, and melted sand becomes glass that helps people see.

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