Find the unit digit of \(7^{71}\).
Answer: B
The power cycle of the unit digit for 7 is (7, 9, 3, 1), with a length of 4. We find the remainder of the power \(71\) when divided by 4. \(71 = 17 \times 4 + 3\). The remainder is 3. The required unit digit is the 3rd in the cycle, which is 3.