Please choose the correct answer to the question: Crows are found throughout many parts of the world. They are black birds with excellent hearing. In the wild they live for six to seven years. Some crows in Japan open hard-shelled nuts by dropping them in front of moving cars. Which of these is a learned behavior?

Answer1: Having excellent hearing Answer2: Living six to seven years Answer3: Dropping nuts in front of cars Answer4: Having black feathers

Answer format: answer1/answer2/answer3/answer4