Which of the following 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,a)−1\text{gcd}(a, a)-1gcd(a,a)−1
gcd(n,m)\text{gcd}(n, m)gcd(n,m)