Social media would be considered an electronic source. This is because it is a source that comes from the internet and can be easily accessed or edited at any time. The rest of the options (ie museum exhibit, interview, and books) may be able to be found online, but generally you must go to a physical location to access the info or have the source physically available.
This means that the answer is B. Social media
Hope this helped!
~Just a girl in love with Shawn Mendes