The correct answer is:
The ones digit repeats from 4 to 6 over and over.
Step-by-step explanation:
4 to the first power is 4.
4 to the second power is 16.
4 to the third power is 64; again the 4 in the ones digit repeats.
4 to the fourth power is 256; again the 6 in the ones digit repeats.
This pattern continues.