Which of the following expressions is a fourth root of unity?

Answer:all of the aboveStep-by-step explanation:If in doubt, multiply them out.   (-i)^4 = i^4 = 1 . . . . . results for ±i   (-1)^4 = 1^4 = 1 . . . . . results for ±1An even power of a negative number is equivalent to the same power of the opposite (positive) number. The even number of minus signs cancel in the final product._____In trig form, unity is 1∠(n·360°) . . . . . for n = any integerThen the 4th root is ...   1^(1/4) ∠(n·360°/4) = 1 ∠(n·90°) . . . . for n = 0...3 (angles repeat after that)That is, the roots are ...1∠0° = 11∠90° = i1∠180° = -11∠270° = -iOf these, all but the first are listed among your answer choices. The appropriate selection is all of the above. (recognizing that not all of the appropriate choices are "above" that answer selection).