In a paper on photosynthesis in a desert cactus in which section would you find a review of existing knowledge that is relevant to the experiment?
a. conclustion
b. materials and methods
c. introduction
d. results

The introduction of a paper usually contains the review of existing knowledge of photosynthesis

Option C

Explanation:

Among this the materials and methods contain a protocol of all experiments that are to be done during a study. The results deals with the results we got from the experiment and the discussion deals with the detailed interpretation of the result. Whereas the introduction deals with the previous study that has taken place.