3 and 4 are correct. A compound is a collection of two or more molecules, whereas a molecule is a collection of two or more atoms. 1 is not true because its talking about two atoms together which is a molecule. 2 is not true because it is still talking about two atoms which is still a molecule. 3 is true because molecule are subunits of compounds. 4 is true because elements and atoms are the same thing, and two or more atoms is a molecule.
