If X and Y are independent then SD (X − Y) is________________?

A. SD(X)−SD(Y)
B. SD(X)+SD(Y)
C. SD(X)+SD(Y)−−−−−−−−−−−−−−√
D. Var(X)+Var(Y)−−−−−−−−−−−−−−−√
18) If Y=−8X − 5 and SD of X is 3, then SD of Y is