Answer:
B: i
Step-by-step explanation:
Algebric explanation: as long as you remember power rules you should be good:
[tex](-i)^3 = (-1)^3\times i^3 = -1 \times i^2\times i= (-1)\times(-1)\times i=1i[/tex]
Geometric explanation: In the complex plane you can think "multiplying by i" as "rotate 1/4 counterclockwise". [tex](-1)^3[/tex] is a real number, and it's simply [tex]-1[/tex]. Rotate that ccw once, you're at [tex]-i[/tex]. Again, and you're at 1. third time (is really the charm!) you end up at [tex]i[/tex].
Polar explanation Courtesy of euler's identity.
[tex](-i)^3 = (e^{-\frac{\pi}2i})^3=e^{-\frac32\pi i}= cos (-\frac32\pi)+isin(-\frac32\pi) = 0+i(1)= i[/tex]
