Which of the Following Is the Best Description of a Podcast

Which of the following is the best description of a podcast?

A) Podcasts are like library card catalogues that users can search electronically to find information they need quickly and efficiently.
B) Podcasts are like radio shows that are distributed through various means and not linked to a scheduled time slot.
C) Podcasts are like newspapers that people can upload to their Smartphones and read anywhere.
D) Podcasts are like calendars that people can use to keep track of the important events in their lives.