Option 1 -> Placid means calm and peaceful, which is the opposite of petulant.
Option 2 -> Patient means tolerant and able to wait calmly, which contradicts the meaning of petulant.
Option 3 -> Irritable means easily annoyed or bad-tempered, which directly matches the meaning of petulant.
Option 4 -> Insignificant means unimportant or trivial, which is unrelated to the emotional state described by petulant.
Hence, Option 3: Irritable -> Petulant describes someone who is childishly sulky, bad-tempered, and easily irritated, making "irritable" the closest synonym. -> correct