Option 1: Imbecile -> refers to someone with low intelligence, not related to complaining behavior.
Option 2: Stoic -> describes someone who endures hardship without complaining, actually the opposite of querulous.
Option 3: Petulant -> means bad-tempered and complaining, shares the same meaning as querulous (habitually whining/complaining).
Option 4: Deficient -> means lacking or inadequate, unrelated to complaining nature.
Hence, Option 3: Petulant -> Both words describe someone who is irritably complaining and whining in nature -> correct