All of the options given are type of sampling, except for (B) availability.
<em>Quota sampling</em> 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. <em>Convenience sampling</em> is a type of sampling where you choose your participants based on availability, or how quickly you can get the data. <em>Random sampling</em> occurs when you are able to get the data for your research population, and from there, determine your sample by randomly choosing them.