Many rural communities in developing countries rely on subsistence economies.

Subsidiary legislation is a type of law that is made by a body or authority under powers given to them by an Act of Parliament.

Perfluoroalkyl substances are widely used in various industrial applications.

Polyfluoroalkyl substances are commonly used in the production of non-stick cookware.

The students' books are on the shelf.

The book's cover is torn.

Subsaharan Africa is known for its diverse cultures and rich natural resources.