Hydroxyurea:

Correct Answer: C

Rationale: Step-by-step rationale: 1. Hydroxyurea inhibits ribonucleotide reductase, leading to decreased DNA synthesis. 2. This action is used in treating conditions like sickle cell anemia, where inhibiting DNA synthesis decreases RBC production. 3. Choice A is incorrect as hydroxyurea actually increases nitric oxide levels. 4. Choice B is incorrect as hydroxyurea decreases WBC production, including neutrophils and monocytes. 5. Choice D is incorrect as hydroxyurea does not increase RBC lifespan but instead decreases RBC production.

Correct Answer: B

Rationale: The correct answer is B: Chemotherapy. In Rai stage II of chronic lymphocytic leukemia (CLL), chemotherapy is the conventional treatment to reduce cancer cells and prevent progression. Antibiotics (choice A) are not the primary treatment for CLL. Antivirals (choice C) are used for viral infections, not CLL. Rest (choice D) alone is not sufficient to treat CLL and may lead to disease progression. Chemotherapy targets cancer cells, making it the appropriate treatment for Rai stage II CLL.

Correct Answer: A

Rationale: The correct answer is A: 70% alcohol or lens cleaner. Alcohol is recommended as it effectively removes oil without damaging the lens. Step 1: Apply alcohol on a clean cloth. Step 2: Gently wipe the lens in a circular motion. Alcohol evaporates quickly, leaving no residue. Xylene (B) is too harsh and can damage the lens. Water (C) can cause streaks and not effectively remove oil. Benzene (D) is toxic and should never be used on optical lenses.

Correct Answer: D

Rationale: Step 1: The Medullary Phase starts in the 6th week of gestation. Step 2: Hematopoiesis starts in the yolk sac and then moves to the liver, spleen, and bone marrow. Step 3: The clavicle is the first bone to show hematopoietic activity during this phase due to its unique development timeline. Step 4: Other choices like the femur, iliac crest, and skull develop hematopoietic activity later in fetal development. Summary: The clavicle is the correct answer as it is the first bone to exhibit hematopoietic activity during the Medullary Phase, while the other choices develop this activity later in the developmental process.

Correct Answer: D

Rationale: The correct answer is D because RBC precursors are located surrounding macrophages near the sinus membrane in the bone marrow. This location allows for the interaction between macrophages and developing RBCs, facilitating the removal of nuclei from maturing RBCs. Choices A, B, and C are incorrect because RBC precursors are not typically found in the center of hematopoietic cords, adjacent to megakaryocytes, or surrounding fat cells in apoptotic islands in the bone marrow.