#### Answer

B

#### Work Step by Step

From the definition of standard deviation:
$\sigma = \sqrt{\dfrac{\sum (x_i-\bar{x})^2}{n-1}}$
Given the values:
$n=4; \bar{x} = \dfrac{8.19+8.22+8.21+8.25}4=8.2175\ g$
Plug this into the standard deviation formula:
$\sigma = \sqrt{\dfrac{(-0.0275)^2+(0.0025)^2+(-0.0075)^2+(0.0325)^2}3}$
$\sigma=0.025\ g$
With the rounding half to even rule it's 0.02 g.