Lesson 6: The invisible machine that keeps ETF prices within pennies of their holdings.$100 of stocks, a $120 price tag.Can the ETF trade at $120 while its stocks are still worth $100?ANot for longA built-in mechanism pulls it back.BYes, easilyAn ETF's price just floats free of what it holds.CYes, and it can stay that far off for months.