Question

multiple choice question
atoms that make up molecules ______.
o must be different
o must be identical
o may be identical or different

Explanation:

Molecules can be composed of the same type of atoms (e.g., oxygen molecule $O_2$ has two identical oxygen atoms) or different - type of atoms (e.g., water molecule $H_2O$ has hydrogen and oxygen atoms).

Answer:

O may be identical or different