When atoms are heated, what is also changing?

Nuclear fusion is the source of energy for stars. besides hydrogen, which other element is most likely also common in stars?

The answer for #3 is c but i don't know why

Five students had to answer the question how are elements arranged in a periodic tabledamon: i think the elements are arranged by increasing massflo: i think the elements are arranged according to their properties sienna: i think the elements are arranged by when their discovers kyle: i think the elements are arranged according to how common they areglenda: i don't agree with any of themwho is right