Lecture 2 (Real Analysis 2020) part 3

To prove that ℕ is itself inductive, what two things must be shown?

1. A.ℕ contains 1, and x ∈ ℕ implies x + 1 ∈ ℕ
2. B.ℕ contains 0, and ℕ has no largest element
3. C.ℕ is bounded, and ℕ is closed under addition
4. D.ℕ is a subset of ℝ, and ℕ contains 1