Verbal - Odd Man Out

DIRECTIONS : In this oddman out section we need choose the word or pair that different from remaining words or pairs.
36. Pick the odd one out
  A.  Uranium
  B.  Polonium
  C.  Sodium
  D.  Radium
37. Pick the odd one out
  A. Peak
  B. Valley
  C. Mountain
  D. Mound

38. Pick the odd one out
  A.  Axe
  B.  Spade
  C.  Hammer
  D.  Blacksmith
39. Pick the odd one out
  A.  Mars
  B.  Mercury
  C.  Earth
  D.  Neptune
40. Pick the odd one out
  A.  Ass
  B.  Donkey
  C.  Camel
  D.  Giraffe