{20,1,6,10,11}
find the subset and the proper subset.

With 5 elements in A={20,1,6,10,11}, there are 2^5=32 possible subsets, including
the null set, and A itself.
Any subset that is identical to A is NOT a proper subset.
Therefore there are 31 proper subsets, plus the subset {20,1,6,10,11}.

The subsets are:
null set  {} (has no elements) total 1
{20},{1},{6},{10},{11}total 5
{20,1},{20,6}...{10,11}total 10
{20,1,6},{20,1,10},...{6,10,11}total 10
{20,1,6,10}...{1,6,10,11}total 5
{20,1,6,10,11}total 1
Altogether 32 subsets.

The correct one is c.