Which statements are correct regarding indexes?

Which statements are correct regarding indexes? (Choose all that apply.)

A.
For each data manipulation language (DML) operation performed, the corresponding indexes
are automatically updated.

B.
A nondeferrable PRIMARY KEY or UNIQUE KEY constraint in a table automatically creates a
unique index.

C.
A FOREIGN KEY constraint on a column in a table automatically creates a non unique key

D.
When a table is dropped, the corresponding indexes are automatically dropped