What is the tens digit of 6^21?	Choose the correct choice from the following choices:  A) 1  B) 3  C) 5  D) 7  E) 9
The tens digit of 6 in integer power starting from 2 (6^1 has no tens digit) repeats in a pattern of 5: {3, 1, 9, 7, 5}:   The tens digit of 6^2=36 is 3.   The tens digit of 6^3=216 is 1.   The tens digit of 6^4=...96 is 9.   The tens digit of 6^5=...76 is 7.   The tens digit of 6^6=...56 is 5.   The tens digit of 6^7=...36 is 3 again.   etc...   21 has the form 5n+1, so the tens digit of 6^21 is 5.   The answer is 5.
<result>C</result>
What is the tens digit of 6^21?