**Core Concept**
Iron deficiency anemia is a common condition characterized by decreased iron stores, leading to reduced hemoglobin production. Oral iron therapy is a primary treatment option, but its effectiveness depends on several factors, including the type of iron preparation, dose, and individual patient factors.

**Why the Correct Answer is Right**
Iron absorption is primarily regulated by the duodenal enterocytes, where it is transported into the bloodstream via the transferrin protein. Oral iron therapy typically uses ferrous salts (ferrous sulfate, ferrous gluconate, or ferrous fumarate), which are more easily absorbed than ferric salts. The optimal dose and duration of therapy vary depending on the severity of anemia, but a common regimen involves 150-200 mg of elemental iron per day for 3-6 months.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the type of iron preparation or the optimal dose.
**Option B:** This option is incorrect because it implies that all iron preparations are equally effective, which is not the case.
**Option C:** This option is incorrect because it suggests that oral iron therapy is not effective for iron deficiency anemia, which is not true.

**Clinical Pearl / High-Yield Fact**
When prescribing oral iron therapy, it is essential to consider individual patient factors, such as gastrointestinal side effects, and to monitor hemoglobin levels regularly to adjust the dose and duration of therapy accordingly.

**Correct Answer: C. Oral iron therapy is effective for treating iron deficiency anemia.**