remarkable inventions, defining relative clauses

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Across
  1. 2. thing that made book printing possible
  2. 3. invention which provided the world with light
  3. 7. where the creator of the telephone is from
Down
  1. 1. brothers who flew the first airplane
  2. 4. last name of man who created the radio
  3. 5. last name of man who created the first automobile, also a name of a popular car brand today
  4. 6. thing that helped discover penicillin