What does a complete blood count (CBC) measure?

A complete blood count (CBC) is a comprehensive blood test that evaluates various components of the blood, providing essential information regarding a person's overall health and helping to diagnose a wide range of conditions.

The correct answer encompasses the measurement of red blood cells (RBCs), hemoglobin, hematocrit, white blood cell counts, and the differential white blood cell counts, which identify the various types of white blood cells present. This detailed information is vital for assessing oxygen transport in the body, immune function, and the presence of conditions like anemia, infections, and many other hematological disorders.

In summary, a CBC provides a broader picture of blood health compared to the other options, which either focus on a limited subset of these parameters or miss key components entirely. This comprehensive nature is what makes option B the most accurate representation of what a CBC measures.