The digit at units place in `2^9^100` is (A) 2 (B) 4 (C) 6 (D) 8

Explanation

`because 9^(100) = (2cdot 4 + 1)^(100) = 4n + 1`
[say]
[where n is positive integer]
`therefore 2 ^(9^(100)) = 2 ^(4n +1) = 2^(4n) cdot 2 = (16)^(n) cdot 2 `
The digit aty unit's place in `(16)^(n) = 6.`
`therefore ` The digit at unit's place in `(16)^(n) cdot 2=2`