With reference to the blood in a normal person, which one of the following statements is correct?

Option 4 is correct: platelets are far more numerous than white blood cells (platelet counts normally range about 150,000–450,000 per microliter) which makes platelets more abundant than leukocytes in blood [1]. Option 1 is incorrect because veins are capacitance vessels and contain the majority of blood volume (almost 60–70% in the venous system), not less than arteries [2]. Option 2 is false: erythrocytes (red cells) make up roughly 40–50% of blood volume (hematocrit ≈45%), so cells do not constitute ~70% of blood volume. Option 3 is wrong since white blood cells develop from hematopoietic stem cells in bone marrow (not only lymph nodes) [3].

Sources

1. [1] https://www.roswellpark.org/cancertalk/202310/understanding-your-blood-test-results
2. [2] https://training.seer.cancer.gov/anatomy/cardiovascular/blood/classification.html
3. [3] https://www.hematology.org/education/patients/blood-basics