Nouns Followed by a Number or Letter

Rule 9.6: Do not use the indefinite article or the definite article with nouns that are immediately followed by a number or a letter.

Route 66 is famous for its beauty.
Where is my next class? It’s in Room 19.
You’re in the wrong area. You need to go to Section C.

Exercise 4: Fill in the blanks with a, an, or Ø.