Final answer:
a) Elevated white blood cell count. A blood sample taken from a patient who has an infection can be expected to show elevated white blood cell count (a) as the immune system responds to the presence of pathogens.
Step-by-step explanation:
A blood sample taken from a patient who has an infection can be expected to show elevated white blood cell count (a) because the body's immune system responds to the presence of pathogens by producing more white blood cells. White blood cells are responsible for fighting off infections and their numbers increase during an infection. Elevated red blood cell count (b) is not typically associated with an infection. Reduced red blood cell count (c) is more commonly seen in conditions like anemia, not infection. Reduced white blood cell count (d) would be an abnormal finding and might indicate a weakened immune system.