If gcd(a,26)=1\gcd(a, 26) = 1gcd(a,26)=1 (meaning aaa is coprime with 26), which of the following must be true?
aaa is odd
aaa is not divisible by 13
There exists an integer xxx such that ax≡1(mod26)ax \equiv 1 \pmod{26}ax≡1(mod26)
All of the above