True Or False Statistics help

a) For independent random variables S and T, Var(S-T) = Var(S)+Var(T).

b) For random variables S and T such that Var(S)>0 and Var(T)>0, we must have Var(S+T)>0.

c) For strictly positive random variables S and T, define Y=S/T.Then, E(Y) is the same as E(S)/E(T).

d) The expected value of perfect information is always strictly positive.

e) The efficiency of sample information can be higher than 1.0.

f) Suppose X is a random variable such that all possible values of X are nonnegative. Furthermore, the expected value of X is 0. Then, the variance of X is always 0.

g) Let Y be a random variable. Then, it is possible to have (E[Y])^2

Thank You