If d=ordn(a)d = \text{ord}_n(a)d=ordn(a), which of the following is true for any kkk such that ak≡1(modn)a^k \equiv 1 \pmod{n}ak≡1(modn)?
k=dk = dk=d
ddd must divide kkk
kkk must divide ddd
kkk is a multiple of ϕ(n)\phi(n)ϕ(n)