singular and plural

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Across
  1. 3. What is the singular of monkeys?
  2. 4. what is the plural of of valley?
  3. 6. what is the singular of toys?
  4. 7. what is the singular of berries?
  5. 8. what is the singular of cities?
  6. 9. what is the plural of birthday?
Down
  1. 1. what is the plural of sky?
  2. 2. what is the plural of bunny?
  3. 5. what is the plural of activity?
  4. 7. what is the singular of babies?