guess that 2nd gen groups!

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Across
  1. 3. 10 out of 10
  2. 5. o.k
  3. 9. irony
  4. 12. come back again
  5. 13. ah!
  6. 15. oh yeah
  7. 17. into the new world
  8. 20. boyfriend
Down
  1. 1. hot issue
  2. 2. replay
  3. 4. break it
  4. 6. i dont know
  5. 7. i want you back
  6. 8. clap
  7. 10. tilt my head
  8. 11. push push
  9. 14. mama
  10. 16. bad girl
  11. 18. gossip girl
  12. 19. superhero