You are correct that if no non-trivial functional dependencies hold in a relation, then the only candidate key is ABCD and the relation is in all four normal forms (1NF, 2NF, 3NF, and BCNF).
A relation is in First Normal Form (1NF) if and only if it does not contain any repeating groups. Since the only functional dependencies in the relation are trivial, there are no repeating groups, and the relation is in 1NF.
A relation is in Second Normal Form (2NF) if and only if it is in First Normal Form (1NF) and every non-key attribute is fully dependent on the primary key. In this case, the only candidate key is ABCD, and all non-key attributes are fully dependent on the primary key, so the relation is in 2NF.
A relation is in Third Normal Form (3NF) if and only if it is in Second Normal Form (2NF) and every determinant in every non-trivial functional dependency is a superkey of the relation. Since there are no non-trivial functional dependencies in the relation, the relation is in 3NF.
A relation is in Boyce-Codd Normal Form (BCNF) if and only if every determinant in every non-trivial functional dependency is a superkey of the relation. Since there are no non-trivial functional dependencies in the relation, the relation is in BCNF.
Therefore, all three options (Option 1: The relation is surely in BCNF, Option 2: The relation is surely in 3NF, and Option 3: The relation is surely in 2NF) are correct.