Given the task definition and input, reply with output. In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.

Question: When was the series of Episode 420 started? Passage:"Episode 420" is the 12th episode in the seventh season of the American animated television series Family Guy. It premiered on Fox in the United States on April 19, 2009. The title of the episode is a reference to the term "420" used in cannabis culture; "Episode 420" premiered on bicycle day, April, 19th, the day before April 20 (4/20), on which a counterculture holiday is celebrated centering on the consumption of cannabis. "420" focuses on the character Brian after he is arrested for drug possession, which prompts him to launch a campaign to legalize cannabis with help from Stewie; the liveliness of their campaign convinces Mayor West to legalize the drug, and most of Quahog's population begins using it.
Links: a. Counterculture b. Cannabis (drug) c. Family Guy (season 7) d. Family Guy
d