Answer:
All answers other than {7, 11, 15, 19}
Explanation:
If we have a Set A, it is a subset of Set B if every element in A is also in B. Set A is a proper subset of Set B if it is a subset of Set B but not equal to Set B.
Using the above information, we know that the proper subset of {7, 11, 15, 19} cannot be itself, so we can rule out the second option.
All of the other options are sets where every element of that set is also an element of {7, 11, 15, 19}. The 3rd option is an empty set, which is a proper subset of any set other than itself, so it is a proper subset of {7, 11, 15, 19}.
Therefore, all of the options except for {7, 11, 15, 19} are valid.