Answer: D. Check Desmos for confirmation. Its your best friend for Graphing.
Step-by-step explanation:
8(4) + 4(4) + 4(2)
32 + 16 + 8
^^ Either one of these two expressions can be written down and they'd both be right.
Why not look up "standard deviation" yourself, to be sure? But yes, the std. dev. is the sqrt of the variance.