Which of the following is the null set ?

Which of the following is a null set ?

Which of the following is a null set

Which of the following is a null set?

Which of the following is a null set?

State which of the following is a null set?

Which of the following is a null set? {x:x in Z and (-1)/(2) lt x lt (9)/(2)} {x:x in N andx-4 le 15} {x:x in N, xlt 5 and x gt 8} {x:x in N and x^(2) lt 40}