Option 1: 5 - 5.5 million Red Blood Cells (RBCs) per mm3 of blood. This means that in a healthy adult man, there are approximately 5 to 5.5 million RBCs in every cubic millimeter of blood.
Option 2: 2 - 2.5 million RBCs per mm3 of blood. This option states a lower range of RBC count compared to the correct answer.
Option 3: 1.5 - 2 million RBCs per mm3 of blood. This option also states a lower range of RBC count compared to the correct answer.
Option 4: 9 - 9.5 million RBCs per mm3 of blood. This option states a higher range of RBC count compared to the correct answer.
The correct answer is option 1, which states that approximately 5 to 5.5 million RBCs are present in a healthy human adult male per mm3 of blood.