The correct answer is A. A relationship is created.
When you drop the primary key of a table into the foreign key of another table, a relationship is created between the two tables. This relationship allows you to join the tables together and view the data from both tables in a single query.
Option B is incorrect because the Edit Relationship dialog box does not appear when you drop the primary key of a table into the foreign key of another table. The Edit Relationship dialog box only appears when you want to edit an existing relationship.
Option C is incorrect because an error does not occur when you drop the primary key of a table into the foreign key of another table. However, if the two tables do not have a compatible data type, an error will occur.
Option D is incorrect because something does happen when you release the mouse pointer after you drop the primary key of a table into the foreign key of another table. A relationship is created between the two tables.