Answer:
d. The scientific literature in his area of interest
Step-by-step explanation:
Scientific literature: The term scientific literature is defined as a concept that encompasses scientific publications that consist of theoretical work and original empirical in the area of social & natural sciences and in the scientific field that is considered as a part of the literature. Scientific literature describes the important and reliable archive related to particular scientific research.
In the question above, the scientific literature in his area of interest can provide the best evidence for a particular study.