Birth during subsistence of marriage is a conclusive proof of legitimacy. This provision is found which following Sections of the Indian Evidence Act?

Section 112 of the Indian Evidence Act deals with the presumption of legitimacy of a child born during the continuance of a valid marriage. According to this section, if a child is born to a woman during the subsistence of a valid marriage or within 280 days after its dissolution, the child is considered to be the legitimate child of that woman's husband unless proved otherwise. This provision establishes a strong presumption of legitimacy based on the birth occurring during the marriage.

Therefore, the correct answer is:
B. Section 112