Final answer:
Option 1). The combining form 'py/o' refers to 'pus', which is linked to various infections and conditions, including pyelonephritis, an infection of the kidneys.
Step-by-step explanation:
The combining form (CF) py/o means pus. Pus is an accumulation of dead pathogens, neutrophils, tissue fluid, and other bystander cells that may have been killed by phagocytes at the site of an infection. The prefix "pyo-" has a meaning related to pus. For instance, the term "pyogenic" in medicine refers to a process that generates pus, while "pyocyst" refers to a cyst that contains pus. It is associated with conditions such as pyelonephritis, which is an infection of one or both kidneys often resulting from a urinary tract infection and can lead to acute renal failure if left untreated.