1. We said that the Context-free languages are a proper subset of the Context-sensitive languages. However, many Context-free grammars are contracting. How can any Context-free grammar be made noncontracting? [Hint: Chomsky Normal Form]

do not use any of these common illegal characters/symbols:

# pound

% percent

& ampersand

{ left curly bracket

} right curly bracket

\ back slash

< left angle bracket

> right angle bracket

* asterisk

? question mark

/ forward slash

  blank spaces

$ dollar sign

! exclamation point

' single quotes

" double quotes

: colon

@ at sign