Which of the following best describes the difference between a mixture and a pure substance?

A.
A mixture is made up of only one type of atom; a pure substance is made up of more than one type of atom.

B.
A mixture has different properties throughout; a pure substance has the same properties throughout.

C.
A mixture has the same properties throughout; a pure substance has the different properties throughout.

D.
A mixture is made up of more than one type of atom; a pure substance is made up of only one type of atom.