You decide to buy a stock for the new year. For the past six years the price has been $120.51, $125.69 $135.65, $158.67, $170.51 and $190.87, for the years 2015 to 2020. What is the standard deviation of the returns of the stock?

a) 4.88%

b) 0.24%

c) 1.26%

d) 2.25%