Identify the type of sampling method that best matches each situation. You may use an answer once, twice, or not at all

1) Surveying every 3rd student coming through the main door to the building

2) Getting a list of every students' name; numbering every name on a list; using a random number generator to select 50 random numbers; and talking to the students those numbers correspond to

3) Selecting five classroom numbers at random then surveying all the students in each of these five rooms