Which of the following expressions is equivalent to GCD(an−1,am−1)\text{GCD}(a^n - 1, a^m - 1)GCD(an−1,am−1)?
aGCD(n,m)−1a^{\text{GCD}(n, m)} - 1aGCD(n,m)−1
aLCM(n,m)−1a^{\text{LCM}(n, m)} - 1aLCM(n,m)−1
GCD(a,n)−1\text{GCD}(a, n) - 1GCD(a,n)−1
aGCD(n,m)+1a^{\text{GCD}(n, m)} + 1aGCD(n,m)+1