I think the correct answer from the choices listed above is option C. The mass of an ice cube is the total amount of water in the ice cube. Ice is the solid form of water. Hope this answers the question. Have a nice day. Feel free to ask more questions.
The answer is B as isotopes are different versions of the same chemical element containing the same amount of protons and electrons but different amounts of neutrons.
#6 should be the independent variable because that's the one you can control
Most likely the answer is water and a salt. When a strong acid and strong base react the OH and H form water and the cation from the base and anion from the acid forms a salt. I hope this helps. Let me know if anything is unclear.