Which two are true about the USING clause when joining tables?

When joining tables in Oracle Database 12c, the USING clause has specific behaviors:

Option C: It is used to specify an equijoin of columns that have the same name in both tables.

The USING clause is indeed used to specify an equijoin between two tables based on columns with identical names in the tables being joined. It simplifies the syntax of the JOIN operation by eliminating the need to qualify the joined columns with table names.

Option D: It can never be used with a full outer join.

The USING clause cannot be used with a full outer join because the full outer join requires a specification of how to treat each side of the join, including rows that don't match the join condition, which is not compatible with the semantics of the USING clause.

Options A, B, and E are incorrect:

Option A is incorrect because when using the USING clause, you do not need to qualify the columns with table names or aliases in the select list; Oracle assumes that they are the same in both tables.

Option B is incorrect because the USING clause can be used with natural joins.

Option E is incorrect as the USING clause is not meant to specify explicit join conditions with operators; it's specifically for equijoins on columns of the same name.