Option D is the only snippet that demonstrates a valid trigger timing and event pairing as commonly tested for DataSys+ objectives around database automation and enforcing data integrity. In mainstream relational databases that support row-level triggers (for example, MySQL/MariaDB-style syntax), triggers are typically defined to fire BEFORE or AFTER a DML event such as INSERT, UPDATE, or DELETE. Option D uses BEFORE UPDATE, which is a recognized pattern: it runs automatically prior to an update operation, allowing the database to enforce business rules or modify values consistently and centrally.
By contrast, ALTER and DROP are DDL operations and are not generally supported as row-level trigger events in common SQL implementations; they are handled through DDL auditing features, event triggers (in specific platforms), or administrative logging—not through FOR EACH ROW triggers. Therefore, options A and C are incorrect for typical trigger usage patterns expected in DataSys+ scenarios. Option B is also invalid because DURING is not a standard trigger timing keyword; the standard model is BEFORE/AFTER (and in some platforms, INSTEAD OF for views).
One typing/logic note: many platforms require referencing the row being modified (for example, NEW.column and OLD.column) rather than bare column names, and trigger bodies often use BEGIN ... END plus statement terminators. Still, among the provided choices, D correctly illustrates the concept DataSys+ emphasizes: using triggers to automate consistent rule enforcement on DML changes.
