Hydroxyurea increases hemoglobin production and decreases reticulocyte cells.

Correct Answer: A

Rationale: Step-by-step rationale for why answer A is correct: 1. Hydroxyurea is a medication used to treat conditions like sickle cell disease. 2. It increases hemoglobin production by stimulating the production of fetal hemoglobin. 3. This increase in hemoglobin levels leads to decreased reticulocyte count. 4. Reticulocytes are immature red blood cells, and their count decreases as hemoglobin production increases. Summary: - Answer A is correct because hydroxyurea does increase hemoglobin production and decrease reticulocyte count. - Answer B is incorrect because hydroxyurea does have these effects. - Answer C is incorrect as these effects are consistent. - Answer D is incorrect as hydroxyurea can have these effects in both adults and children.

Correct Answer: A

Rationale: Rationale: 1. Absolute lymphocytosis >5000/mm^3 without other symptoms indicates low tumor burden. 2. In Rai Staging System, Stage 0 represents low risk with lymphocytosis only. 3. No adenopathy, hepatosplenomegaly, anemia, thrombocytopenia rules out higher stages. 4. Hence, the correct answer is A: Stage 0. Other choices are incorrect due to absence of additional symptoms.

Correct Answer: A

Rationale: The correct answer is A: Tense. In the tense form of the hemoglobin (Hb) molecule, the binding of oxygen is hindered, leading to low oxygen affinity. This form occurs in tissues where oxygen is needed, promoting oxygen release. The relaxed form (choice B) has higher oxygen affinity, favoring oxygen binding. Arterial (choice C) and venous (choice D) refer to the oxygen saturation levels in blood, not directly related to the oxygen affinity of Hb molecules.

Correct Answer: C

Rationale: The correct answer is C: Polarizing microscopy. Polarizing microscopy is valuable in identifying crystals that rotate light because it can distinguish between isotropic and anisotropic materials, such as crystals. When polarized light passes through an anisotropic material like crystal, the light waves are split into ordinary and extraordinary rays, causing the crystals to rotate light. This phenomenon, known as birefringence, is observed under polarizing microscopy. Incorrect Choices: A: Compound brightfield microscopy does not provide the necessary contrast to identify crystals that rotate light. B: Darkfield microscopy is used for observing light scattering, not for identifying crystals that rotate light. D: Phase-contrast microscopy is used to enhance contrast in transparent samples, not specifically for identifying crystals that rotate light.

Correct Answer: D

Rationale: The correct answer is D: Liver. During midfetal life, the liver is the primary source of blood cells. The rationale behind this is that the liver is the major site of hematopoiesis during this developmental stage, producing red blood cells, white blood cells, and platelets. The liver's hematopoietic function gradually declines as the bone marrow takes over this role postnatally. Explanation for why other choices are incorrect: A: Bone marrow - While bone marrow becomes the primary site of hematopoiesis in adults, during midfetal life, it is not the main source of blood cells. B: Spleen - The spleen plays a role in blood filtration and immune response, but it is not the primary source of blood cells during midfetal life. C: Lymph Nodes - Lymph nodes are important for immune function and lymphocyte production, but they do not serve as the primary source of blood cells during midfetal life.