A peripheral blood smear can reveal what aspect of red blood cells?

A peripheral blood smear is a technique used to examine the morphology of blood cells under a microscope. When evaluating red blood cells (RBCs), this method can reveal variations in size (anisocytosis) and shape (poikilocytosis). Such variations may indicate different pathological conditions, such as anemia, thalassemia, or other hematological disorders.

While platelets are indeed present in a blood smear, the primary focus of a smear is to assess the characteristics of the red blood cells rather than the platelets. Vitamin levels and blood pH cannot be directly assessed through a peripheral blood smear; these measurements require specific biochemical tests conducted in a laboratory setting. Thus, the distinguishing feature that can be evaluated through a peripheral blood smear relates specifically to the variations in size and shape of red blood cells, making this the correct answer.