The query's goal is to return a list of countries that have no departments linked to them.
Option B and Option D are the correct answers because they use set operations that will effectively return countries that do not have a corresponding entry in the departments table:
* Option B uses the NOT IN subquery to exclude countries that have departments linked to them. It looks for country_id values in the countries table that are not present in the list of country_id values associated with locations that are, in turn, associated with departments. This will correctly return countries that have no departments.
* Option D uses the MINUS set operator, which subtracts the results of the second SELECT statement from the results of the first. This statement will return all countries from the countries table minus those that have an associated department_id in the departments table, effectively listing countries with no departments.
Option A and Option C are incorrect because:
* Option A will not execute successfully as it tries to join tables using a column (country_id) that doesn't exist in the departments table, which will lead to an error.
* Option C's use of INTERSECT is incorrect for this requirement. INTERSECT returns only the rows that exist in both queries. Since we want countries with no departments, using INTERSECT would actually return the opposite of what is required.
References:
* Oracle Documentation on NOT IN clause: SQL Language Reference - Subquery
* Oracle Documentation on MINUS operator: SQL Language Reference - Set Operators Therefore, the correct options are B and D, which use subquery exclusion and the MINUS set operator, respectively, to accurately identify and return countries without departments.