Students in chemistry course were asked the following question on a unit exam: "Draw a diagram representing an element using circles as atoms."
a. The following diagrams represent the two types of answers given by students. Which is the drawing best representation of an element? Explain.
b. imagines that the atom in drawing B had been removed from one of the substances used earlier.
i. List the codes of the substances that "drawing B" could have come from through physical separations?

I need more help with part b. plz