Which group of statements best describes all of the same materials he is using in the investigation

A scientist is conducting an investigation that involves water, silver, carbon dioxide, and oxygen gas.  

Which group of statements best describe all of the materials he is using in the investigation?

A) They are each compounds. Each of the compounds is made of atoms. All of the atoms are made of matter.

B) They are each made of matter. Some are compounds and some are elements. They all contain atoms.

C) They are all elements. Some contain molecules of the same type of atom. Some contain different types of atoms.

D) They are each made of matter. Some are compounds made of one type of element. Some are pure atoms.

Answer D) is correct