A scientist finds that a sample of matter contains three types of atoms. The sample can be any of the following, except: A. compound
B. molecule
C. element
D. mixture

The correct answer is C. element

Explanation:

The sample cannot be an element because an element - or elemental substance - cannot be decomposed into simpler substances. Thus, it cannot be composed by differents types of atoms. For example, an element is carbon (C).

As the sample contains three types of atoms, it can be a compound, a molecule or a mixture, because they can be composed by different types of atoms - of different chemical elements. For example, the sample could contain the element carbon (C) combined with other elements, for example oxygen (O) or hydrogen (H), amoing others.