How were redi’s and pasteur’s experiments different?
a. redi studied broth, but pasteur tested meat.
b. pasteur studied flies, but redi tested meat.
c. pasteur tested for microorganisms, but redi studied larger organisms.
d. redi tested for microorganisms, but pasteur studied larger organisms

The answer to the question stated above is letter c. Pasteur tested for microorganisms, but Redi studied larger organisms.

Redi experimented with rotting meat; Pasteur experimented with broth. Redi disproved spontaneous generation for large organisms by illustrating that maggots arose from meat only when flies laid eggs in the meat.  Pasteur used his famous swan-neck flask experiment, to end the debate. On his experiment  air is allowed to contact the broth. Microbes present in the dust were not able to navigate the tortuous bends in the neck of the flask. 

Ithink the answer is d.