To answer this question, we need to know the background and history of Kurt Cobain.
Kurt Cobain was the lead vocalist and guitarist of the American rock band Nirvana. Before achieving fame, Cobain lived in various places and had different roommates.
Option A) Krist Novoselic - Krist Novoselic is a musician and was a founding member and bassist of Nirvana. While Novoselic and Cobain were bandmates, they were not roommates.
Option B) Toby Vail - Toby Vail is a musician and was part of the Riot Grrrl movement. She had a relationship with Cobain, but there is no information suggesting that they were roommates.
Option C) Lamont Schillinger - Lamont Schillinger is a fictional character from the TV series "Oz." This option is incorrect as Schillinger is not a real person and therefore was not Cobain's first flat mate.
Option D) Courtney Love - Courtney Love is a musician and actress who was married to Kurt Cobain. While she was a significant part of Cobain's life, she was not his first flat mate.
Therefore, the correct answer is none of the given options.