How can a mixture of nails and sawdust be most efficiently separated into its component parts? a: by cooling it b: by filtering it c: by using a magnet d: by using a catalyst

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