💡 Detailed Explanation
The adverb 'だんだん' (dandan) means 'gradually' or 'little by little' and describes a continuous, gradual change over time. It is always paired with verbs indicating change (e.g. '〜になる' - to become, '〜ていく' - to go on doing). Option 2 is correct: 'Gradually, my Japanese became better.' Option 1 is incorrect because getting hungry ('おなかがすきました') is usually expressed as a sudden realization (would use 'すいてきた' with 'だんだん', not the past 'すきました'). Options 3 and 4 describe sudden, one-time events ('train arrived', 'movie started') where gradual change is not applicable.