What of the Following Is the Best Approach to Deciding

What of the following is the best approach to deciding on the number of bins for a histogram?

A) The number of bins should be approximately 20% of the number of data values.
B) There is a formula, number of bins = 1 + ln(n) /ln(2) , that should always be used to set the number of bins.
C) There is no strict rule; the number of bins should be chosen to best show patterns.
D) There should be no less than 5 bins and no more than 20.