You can use the appropriate citation option from below to add a reference to this page.
"21D." Fullformexpand.com, https://www.fullformexpand.com/21d/1026939. Accessed 23 Nov. 2025.
Fullformexpand.com, 2025. "21D." Accessed November 23, 2025. https://www.fullformexpand.com/21d/1026939.
"21D." (n.d.). Fullformexpand.com. Retrieved November 23, 2025, from https://www.fullformexpand.com/21d/1026939.
21D. (2025). Fullformexpand.com. Available at: https://www.fullformexpand.com/21d/1026939 (Accessed: 23 November 2025).