The correct option is C Z={a,n,t,r,c,o}
For Roster form of sets, we know that both the order and repitition of the elements is immaterial.
Hence, utilizing these two properties, we can represent the set as:
Z={c,o,n,t,r,a}
Since order does not matter, we can also represent the set as: Z={a,n,t,r,c,o}
Also, Z≠{c,o,n,r} as it does not contain all the letters of the word.