Sub AnswerLetterChange()
With ActiveDocument.Content.Find
  .ClearFormatting
  .Replacement.ClearFormatting
  .Forward = True
  .Wrap = wdFindContinue
  .Format = False
  .MatchWildcards = True
  .Text = "<([A-D]):"
  .Replacement.Text = "\1."
  .Execute Replace:=wdReplaceAll
End With
End Sub