Complete Residue of n
Trivia · proposed by @vipproaccout
Which of the following is not a property of a complete residue system modulo $n$?
AIt has exactly $n$ elements.
BIt contains exactly $2$ elements that are congruent to each other modulo $n$.
CMultiplying every element of the system by an integer coprime to $n$ produces another complete residue system modulo $n$.
DAdding a fixed integer to every element of the system produces another complete residue system modulo $n$.