A Mining Share for a Company Listed on the ASX

A mining share for a company listed on the ASX produced returns of 19 per cent,27 per cent,and -38 per cent over three of the past four years.The arithmetic average for the past four years is 7 per cent.What is the standard deviation of the stock's returns for the four-year period?

A) 11.63 per cent
B) 15.94 per cent
C) 19.70 per cent
D) 26.25 per cent
E) 30.21 per cent