Probably be C then, since it would be st dev of any range of 18 consecutive even integers, which I think always be equal.
A: INSUFF (what even integers?)
B: INSUFF (Range tells 18, but other numbers are not known)
A & B: INSUFF (10 even integers with range 18 but they may not be consecutives and there can be repetitions)
if the question were to be: distinct even integers?
it could be distinct integers with a range of 18 or some distinct and some repetitive integers with the same range. for ex:
a: 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20
b: 2, 2, 6, 8, 10, 12, 14, 16, 18, and 20
in above cases, a and b have different Standard Deviations but fulfill both requirements in st. 1 and 2.
so only E makes sense.