'Chocolate tasted like nectar' uses 'like' for comparison, so it is a simile (A-IV). 'Dark light' combines contradictory terms, making it an oxymoron (B-II). 'Going great guns' repeats the 'g' sound, making it alliteration (C-III). 'Young Major is the sunshine of the brigade' equates a person to sunshine directly, making it a metaphor (D-I). This matches option 2.