Which of the Following Would Be an Example of the Type

Which of the following would be an example of the type of data known as "available data"

A) administering a questionnaire to the college students available to the researcher in her classes
B) using information in the files of a social service agency to study the social factors associated with unwanted pregnancies
C) using an availability sample as a means of collecting subjects for an experiment
D) making unobtrusive observations of inmates of a prison during their recreation periods