4iii.
A non-trivial subgroup needs to contain the identity element
and, in this case, one, two or three other elements.
Remember that a subgroup must be closed, so if you have the element a in
your subgroup, you must also have a * a.
The first group contains the non-trivial subgroups
{e,a},
{e,b},
{e,c}, and {e,a,b,c} (the entire group).
The second group contains the non-trivial subgroups
{0,2} and {0,1,2,3} (the entire group).