To answer this question, you need to understand how foreign key constraints work in a database.
Foreign key constraints are used to enforce referential integrity between tables in a database. When a foreign key constraint is defined between a parent table and a child table, it ensures that any value in the child table's foreign key column must exist in the parent table's primary key column.
When you want to drop a parent table that has foreign key constraints with a child table, you need to first drop the foreign key constraints in the child table. This is because the child table's foreign key constraints reference the parent table's primary key, and you cannot drop the parent table if the child table still has references to it.
The clause that enables you to drop the foreign key constraints of the child table while dropping the parent table is "cascade constraints."
Option A) drop foreign keys - This option is incorrect because there is no such clause in Oracle to drop foreign keys directly. You need to use "cascade constraints" to drop the foreign key constraints.
Option B) cascade constraints - This option is correct. It allows you to drop the foreign key constraints of the child table while dropping the parent table.
Option C) this is not possible in Oracle - This option is incorrect. In Oracle, you can drop the foreign key constraints of the child table using "cascade constraints" clause.
Option D) clear references - This option is incorrect. "Clear references" is not a valid clause in Oracle for dropping foreign key constraints.
The correct answer is option B. The "cascade constraints" clause enables you to drop the foreign key constraints of the child table while dropping the parent table.