Which of the following can be separated by physical methods?

The correct answer is mixtures. Mixtures are formed when two or more substances are combined without undergoing any chemical change, meaning that each component retains its individual properties. Because of this characteristic, the components of a mixture can be separated by physical methods, which might include filtration, distillation, or centrifugation, depending on the nature of the mixture.

Elements are pure substances that cannot be broken down into simpler substances by chemical or physical means. Compounds, on the other hand, are chemically bonded combinations of elements that can only be separated into their constituent elements through chemical reactions, not physical methods. Alloys, which are also mixtures, involve a combination of metals (and potentially non-metals), but since they often involve specific proportions and metallic bonding characteristics, their separation can still require more advanced methods that might not classify as simple physical separation.

By understanding the nature of mixtures and how they can be manipulated through physical techniques, it's clear why they are distinct from elements, compounds, and alloys.