Final answer:
The items from the Louis Pasteur experiment are matched to their functions: Beef broth provides a growth environment, a Bunsen burner flame sterilizes, a swan-neck flask traps airborne contaminants, and air is a source of potential contaminants.
Step-by-step explanation:
The Louis Pasteur experiment is fundamental in microbiology and provides an excellent teaching point for understanding aseptic techniques and microbial growth.
The matching of items to their functions in Pasteur's experiment is as follows: 1) Beef broth matches with letter a) provided a nutritious environment to support microbial growth.
2) Bunsen burner (flame) matches with letter d) provided heat that destroyed microorganisms already present in the beef broth.
3) Flask with S-shaped neck, which is also known as a swan-neck flask, matches with letter b) provided the physical conditions for trapping airborne contaminants and preventing microorganisms from entering the flask.
Lastly, 4) Air matches with letter c) provided a source of potential external microbial contaminants.
Pasteur's ingenious design allowed for the passage of air while preventing the entry of airborne microorganisms, which supported his argument against the theory of spontaneous generation and laid the groundwork for the germ theory of disease.