半衰期的問題

[smoth (MASTER!! )]

  The number of half-lives needed for a radioactive element to decay to
  about 6% of its original activity is
  A)2  B)3 C)4  D)5  E)6



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◆ From: 218.165.132.219
→ yacat:100→50→25→12.5→6.25 ，所以衰變了四次。