Please choose the correct answer to the question: After mining removes layers of rock from a hillside, new plants begin to grow in the cracks of the bare rock. The plants beginning to grow are an example of which natural process?

Answer1: secondary succession in an existing ecosystem Answer2: new species developing in an ecosystem Answer3: species competition in a community Answer4: primary succession in a new habitat

Answer format: answer1/answer2/answer3/answer4
Answer: answer4