Substance a doesn't have fixed melting and boiling points substance b has fixed melting and can't be broken down by chemical reaction substance c has fixed melting and boiling points and breaks down into simpler substances when heated

Which best describes the present-day universe? opaque, expanding very slowly, stars produce heavy elements transparent, expanding at an accelerated rate, stars produce heavy elements opaque, expanding at an accelerated rate, stars produce only hydrogen and helium transparent, expanding very slowly, stars produce only hydrogen and helium