Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

Lindstrom's theorem states that first-order logic is the strongest logic having both this property and satisfying the Lowenheim-Skolem property. A method for finding a Hausdorff space with this property containing a given space is named for Stone and Cech. Equicontinuity is the main condition for determining whether a family of functions has this property by the Arzela-Ascoli theorem. Using the axiom of choice, it can be shown that an arbitrary product of spaces with this property has this property, a result known as Tychonoff's theorem. In Euclidean space, being closed and bounded is sufficient to show, according to the Heine-Borel theorem, that a set has this property. For 10 points, identify this property which holds of a set on which every open cover has a finite subcover.
Science