**Core Concept**
This patient presents with symptoms suggestive of a hematological disorder, specifically anemia and thrombocytopenia, with a normal MCV, indicating a normocytic anemia. The underlying principle being tested is the identification and differentiation of various types of anemia and thrombocytopenia.

**Why the Correct Answer is Right**
The patient's presentation of normocytic anemia and thrombocytopenia, with a normal MCV, is suggestive of Bone Marrow Failure Syndrome (BMFS). This condition is characterized by the failure of the bone marrow to produce blood cells, leading to a reduction in the production of erythrocytes, leukocytes, and platelets. The presence of a normal MCV rules out iron deficiency anemia or other types of anemia that may cause microcytosis or macrocytosis. The correct approach to diagnosis involves a comprehensive evaluation of the patient's bone marrow function.

**Why Each Wrong Option is Incorrect**
**Option A:** Ordering a complete blood count (CBC) is essential but not sufficient for the diagnosis of BMFS. A CBC can provide information on the type and severity of anemia and thrombocytopenia, but it does not provide a definitive diagnosis.
**Option B:** Performing a liver function test is not relevant to the diagnosis of BMFS. Liver function tests may be abnormal in patients with liver disease, but they do not provide information on bone marrow function.
**Option C:** Conducting a physical examination is essential in the evaluation of any patient, but it is not sufficient for the diagnosis of BMFS. A physical examination may reveal signs of anemia, such as pallor or fatigue, but it does not provide a definitive diagnosis.
**Option D:** Ordering a CT scan of the abdomen is not necessary for the diagnosis of BMFS. A CT scan may be useful in evaluating the cause of anemia or thrombocytopenia, such as a bleeding ulcer or a tumor, but it is not a necessary step in the diagnosis of BMFS.

**Clinical Pearl / High-Yield Fact**
BMFS is a rare condition that can be caused by a variety of factors, including autoimmune disorders, infections, and exposure to toxins. It is essential to consider BMFS in the differential diagnosis of patients with unexplained anemia and thrombocytopenia.

**Correct Answer: A. Bone marrow biopsy and aspiration to evaluate bone marrow function.**