# Which of the following is NOT a valid ACME challenge type?

cert-manager, Medium (Advanced), Concepts. https://k8wiz.com/uquiz/which-of-the-following-is-not-a-valid-acme-challenge-type

- A. HTTP-01
- B. DNS-01
- C. TLS-ALPN-01
- D. EMAIL-01

**Answer:** EMAIL-01

**Explanation:** EMAIL-01 is not a valid ACME challenge type. The valid ACME challenge types supported by cert-manager are HTTP-01 (which uses HTTP endpoints), DNS-01 (which uses DNS records), and TLS-ALPN-01 (which uses TLS Application-Layer Protocol Negotiation).