The Mo You Know with Greek and Roman Numerals

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Across
  1. 1. A null account's root is _and means no, none
  2. 2. A _agon has 7 sides
  3. 4. This means 100 and a half ____ centennial
  4. 6. 2011 was a what- - - -de ago?
  5. 8. A uniform makes a team _?
  6. 9. A septet has_ member?
  7. 11. Halloween is in ___ber?
  8. 12. This is 55 in roman numerals.
  9. 14. This year in Roman numerals
  10. 16. pregnancy is divided into a _mester
  11. 17. A semicircle is what of a circle?
Down
  1. 1. To annihilate something is to make it _?
  2. 3. A prototype is a _ of its kind?
  3. 5. Decibels is on a scale of 1 to _?
  4. 7. This means both a- - -?
  5. 9. Solitary is a game played _?
  6. 10. The upcoming Superbowl in 2022 is Superbowl L- -
  7. 13. Earth is cut into _ hemispheres?
  8. 15. This number is at the top of Big Ben's Clock Face X_ _.
  9. 16. Duet includes _ people?
  10. 18. Steve Irwin died this year (10 years from 2016)