Which is a characteristic of mixtures?

A. They are chemically bonded together.

B. They can be classified as pure substances.

C. They have fixed ratios between their components.

D. They can be separated by physical processes.

I would say D) They can be separated by physical processes. Imagine a mixture of sand and salt. You can separate the salt by adding the mixture to water and dissolving it. you then decant (pour off) the salt water and evaporate the water, leaving just salt.