MgCl2 would be magnesium chloride.
Answer: sunlight
Explanation:
They get carbon dioxide from the sunlight, in a process called photosynthesis. They absorb the sunlight and turn the energy into carbon dioxide.
Crystsals can precipitate out of solution when some of the solvent is evaporated. For example, if you have sodium chloride in solution and you evaporate out the water some sodium chloride crystals will form. I hope this helps. Let me know if anything is unclear.
Gold is a chemical element with the place on the periodic table of AU (from Latin aurum.) It is a pure form of metal, making it a conductor. As you know, metal is a conductor. It does retain its conductivity due to the lack of tarnishing. Though silver and copper are better with conducting, gold would make a decent conductor.