Solve the Problem. -How Many 2-Letter Codes Can Be Formed Using the Letters

question 54

Multiple Choice

Solve the problem.
-How many 2-letter codes can be formed using the letters A, B, C, D, E, F, G, H, and I. Repeated letters are allowed.

• A) 36
• B) 72
• C) 512
• D) 81

---

Definitions:

Phagocytosis

The process by which a cell engulfs particles such as bacteria or cellular debris to digest them.

Antigens

Substances (often proteins) on the surface of cells, viruses, fungi, or bacteria that the immune system recognizes and targets.

Lymphatic Capillaries

Small, thin-walled vessels that are the starting point of the lymphatic system, responsible for the absorption of interstitial fluid and its return to the bloodstream.

Autoimmune Diseases

Conditions where the immune system mistakenly attacks the body's own cells, leading to inflammation and tissue damage.