**Core Concept**
Iron deficiency anemia is characterized by low serum iron levels, low hemoglobin, and low serum ferritin, indicating depleted iron stores. The mean corpuscular volume (MCV) is decreased, indicating microcytic anemia.

**Why the Correct Answer is Right**
The combination of low serum iron, low hemoglobin, and low serum ferritin levels confirms iron deficiency anemia. Serum ferritin is a reliable indicator of iron stores, and a level below 15 ng/mL is diagnostic of iron deficiency. In this case, the serum ferritin is 100 ng/mL, which is significantly below normal, indicating depleted iron stores. The low serum iron and low hemoglobin levels further support the diagnosis of iron deficiency anemia. The low MCV suggests that the anemia is microcytic.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a clear diagnosis based on the lab values provided.
**Option B:** This option is incorrect because it does not match the lab values provided. A diagnosis of anemia of chronic disease would typically be associated with normal or elevated serum ferritin levels.
**Option C:** This option is incorrect because it does not provide a clear diagnosis based on the lab values provided.

**Clinical Pearl / High-Yield Fact**
In cases of iron deficiency anemia, serum ferritin levels are a crucial diagnostic tool. A level below 15 ng/mL is diagnostic of iron deficiency, and levels between 15-30 ng/mL indicate mild iron deficiency.

**Correct Answer: C. Anemia of chronic disease is characterized by elevated serum ferritin levels and is typically associated with chronic illnesses such as chronic kidney disease or rheumatoid arthritis.