What Is the Procedure for Selecting a Snowball Sample

What is the procedure for selecting a snowball sample?

A) You select your sample through a random sampling procedure such as the one where you select the fifth person from your list and every fifth person thereafter.
B) You select a rolling list of people for your sample by including not only those who asked for service today but also those who ask for service tomorrow and the next 3 days.
C) You select a sample from the list of the members of a particular organization.
D) You select a sample from a given location, then ask those selected to identify other people who are like them and you include these other individuals in your sample.