Solution

Under the Indian Evidence Act, 1872, Section 112 provides for the presumption of legitimacy of a child born during the subsistence of a valid marriage. This presumption is a legal presumption, also known as a presumption of law, which means that the court is required to presume that the child is the legitimate child of the husband and wife. This presumption of legitimacy arises when the child is born during the subsistence of a valid marriage, and the husband and wife are living together as husband and wife at the time of the child's birth. This presumption can be rebutted by evidence to the contrary, such as evidence showing that the husband was not the biological father of the child. It is important to note that this presumption is not an absolute presumption, and can be rebutted by evidence to the contrary. However, the burden of proving that the child is illegitimate is on the person challenging the presumption of legitimacy.