All of the options given are type of sampling, except for (B) availability.
Quota sampling is a type of sampling where you determine the number of participants you need to get a valid data for your research, which is normally done using a certain formula. Convenience sampling is a type of sampling where you choose your participants based on availability, or how quickly you can get the data. Random sampling occurs when you are able to get the data for your research population, and from there, determine your sample by randomly choosing them.
