Which of the following expressions result in a real number?
(−8)2/3(-8)^{2/3}(−8)2/3
(−16)1/2(-16)^{1/2}(−16)1/2
(−32)1/5(-32)^{1/5}(−32)1/5
(−1)3/4(-1)^{3/4}(−1)3/4