Step 1: Understanding the Question
The question asks to identify the specific Indian law that defines the age of majority, stating that a person who has not completed 18 years is a minor.
Step 2: Analyzing the Acts
(A) Negotiable Instrument Act: Deals with instruments like cheques, promissory notes, and bills of exchange. It does not define the age of majority.
(B) Indian Contract Act: This act states that a minor is not competent to contract, but it does not provide the general definition of who a minor is. It relies on the definition provided by the law to which the person is subject.
(C) Indian Evidence Act: This act contains the rules of evidence applicable in Indian courts. It does not define the age of majority.
(D) Indian Majority Act, 1875: This is the specific law enacted to provide a uniform definition for the age of majority for all persons domiciled in India. Section 3 of this Act explicitly states that every person shall attain the age of majority on his completing the age of eighteen years and not before, except in cases where a guardian has been appointed by a court.
Step 3: Final Answer
The Indian Majority Act, 1875 is the law that defines a minor as a person who has not completed the age of 18. Therefore, option (D) is the correct answer.