Which of the Following Is an Example of Systematic Research

Which of the following is an example of systematic research?

A) Karenna cannot remember the name of a song that is stuck in her head, so she does an internet search for the lyrics, which helps her find the song title.
B) Jeremy wants to find the best pizza shop in the city where he has just moved, so he asks his co-worker, who has an Italian last name.
C) Kelsey wants to know how viewers feel about reality TV stars, so she asks 50 reality TV stars to let her read, code, and analyze their fan mail.
D) Jeff wants to be supportive of his best friend, who lives with and battles depression. Jeff spends a lot of time reading articles from books, magazines, and blogs about how to support someone with depression.