If XXX is a random variable, is E[X2]≥(E[X])2E[X^2] \geq (E[X])^2E[X2]≥(E[X])2 always true?
Yes, always.
No, only if E[X]>0E[X] > 0E[X]>0.
No, it is only true for discrete variables.
Never true.