Explanation:

In a new firm, there are certain legal requirements and restrictions regarding who can be a partner. Among the options given, only a married woman can be a partner in a new firm. Let's discuss each option in detail:

a) Minor:
A minor is a person who has not yet attained the age of majority, which is typically 18 years. Minors are not capable of entering into a valid partnership agreement as they lack the legal capacity to do so. They are considered to be incompetent to contract, and any agreement entered into by a minor is voidable at their option.

b) Alien enemy:
An alien enemy refers to a person who is a citizen or national of a country that is at war with the country in which they reside. In most jurisdictions, an alien enemy is prohibited from engaging in commercial activities, including being a partner in a firm, as it may pose a threat to national security or interests.

c) Lunatic person:
A lunatic person is someone who is mentally ill or insane. In general, a person who is of unsound mind is not capable of entering into a valid partnership agreement as they lack the mental capacity to understand and execute the terms of the partnership contract.

d) Married woman:
A married woman, on the other hand, can be a partner in a new firm. In the past, there were certain legal restrictions on married women's ability to engage in business activities. However, with the advancement of gender equality and women's rights, these restrictions have been lifted in many jurisdictions. Nowadays, married women have the same legal capacity as their husbands and can freely enter into partnership agreements.

In conclusion:
Among the options given, only a married woman can be a partner in a new firm. Minors, alien enemies, and lunatic persons do not have the legal capacity to enter into a valid partnership agreement. It is important to comply with the legal requirements and restrictions when forming a new firm to ensure the validity and enforceability of the partnership agreement.