Which of the following are complete residue systems modulo $11$? Which of the following are complete residue systems modulo 11?
$(a)\quad  0,1,2,4,8,16,32,64,128,256,512$
$(b)\quad  1,3,5,7,9,11,13,15,17,19,21$
$(c)\quad  2,4,6,8,10,12,14,16,17,20,22$
$(d)\quad  -5,-4,-3,-2,-1,0,1,2,3,4,5$
I have the answer which is that they are all complete residue systems modulo 11. However, I do not fully understand the definition of residue system or how to determine what sets make up a complete residue system?

The set of integers {0, 1, 2, ..., n - 1} is called the least residue system modulo n. Any set of n integers, $\bf no\ two\ of\ which\ are\ congruent\ modulo\ n$, is called a $\bf complete\ residue\ system\ modulo\ n$.
http://en.wikipedia.org/wiki/Complete_residue_system_modulo_m#Residue_systems
{0,1,2,3,4,5,6,7,8,9,10} is a complete residue system modulo 11. 
Since $1 \equiv 12 \pmod{11}$,$3 \equiv 14 \pmod{11}$, ... , $10 \equiv 21 \pmod{11}$.
After dividing 11 for each of them, the residues are:
(a)0,1,2,4,8,5,10,9,7,3,6;
(b)1,3,5,7,9,0,2,4,6,8,10;
(c)2,4,6,8,10,1,3,5,6,9,0; (c isn't)
(d)6,7,8,9,10,0,1,2,3,4,5.
