Which statement about mixtures and compounds is TRUE?

Physical separation methods like filtration can be used to separate the components of a compound, whereas physical methods cannot be used to separate the components of a mixture.

The components of a mixture do not change when separated, whereas the components of a compound do change when separated.

Compounds are composed of only one type of atom, whereas mixtures are made up of several types of atoms.

The ratio of components in a compound is not fixed, whereas the ratio of components in a mixture is fixed.