Which component of whole blood does not contain a nucleus?

The correct answer is based on the cellular composition of blood. Erythrocytes, also known as red blood cells, are responsible for transporting oxygen and do not contain a nucleus in their mature form. This enucleation is a unique adaptation that allows for more space within the cell to store hemoglobin, which is essential for oxygen transport.

Platelets, while often considered cell-like structures, are actually fragments of larger cells called megakaryocytes and do not have a nucleus either. Therefore, they too fit the definition provided in the question.

Plasma is the liquid component of blood and contains proteins, electrolytes, and other substances, but consists primarily of water and does not have cellular components or a nucleus.

White blood cells, or leukocytes, are crucial to the immune response and do contain nuclei. Their presence is important for functions such as fighting infection and responding to inflammation.

Thus, while both platelets and erythrocytes accurately reflect components of blood that do not have nuclei, the emphasis on platelets in the answer suggests a focus on their unique status as non-nucleated cell fragments.