Question:When can an American style option be exercised?
  A. On any day up to and including the expiry date.
  B. On any day up to but excluding the expiry date.
  C. On the expiry date only.
  D. Within the five day settlement period commencing on the expiry date.
  The correct answer is: On any day up to and including the expiry date.
  Note that most options traded in the UK and Europe are in fact American options.