I think it is the second one! I am pretty sure!
Start your introduction broad, but not too broad, Provide relevant background, but don’t begin your true argument,Provide a thesis, Provide only helpful, relevant information, Try to avoid clichés, Don’t feel pressured to write your intro first, Convince the reader that your essay is worth reading.
'Before' is an adjective. This is because it describes the time.
So, the answer would be: B. adjective phrase
