The Answer is D cause of the people going back and forth.
2. Rubidium
3. Antimony
4. Ytterbium
5. Einsteinium
B is your best answer because a mixture is when two or more things combine but not chemically. Take soup for example you take out all the pieces because they didn't combine together and just become 1 thing they still have parts. You can still take the noodles, you take the fish or meat out still, you take the broth away to.
