A "Gallup poll" is a national public opinion poll run by Gallup, Inc. According to the company's website, a typical sample size for a phone-based Gallup poll is 1000 randomly-selected adults, and poll results are said to be representative of the opinions of all Americans within a margin of error of ±4 percentage points. What methods do you think Gallup, Inc. must use to ensure true random selection of all 1000 phone participants? Give at least 3 methods.