Complete the notes below.
Write NO MORE THAN THREE WORDS or A NUMBER for each answer.
  Braille-a system of writing for the blind
Louis Braille was blinded as a child in his 21 ........................
Braille invented the writing system in the year 22 ......................
An early writing system for the blind used embossed letters.
A military system using dots was called 23 ........................

21（）