Explanation:

- Option 1: Not a legal person

The United Nations (UN) is recognized as a legal entity, able to engage in legal actions such as entering contracts or bringing about litigation. This option is incorrect.

- Option 2: A legal person

The UN is indeed considered a legal person under international law, possessing rights and duties. It can perform legal actions necessary for fulfilling its objectives.

- Option 3: Legal person on the disserting S of Secretary General

The Secretary-General does not control the legal status of the UN. This option is irrelevant.

- Option 4: Legal person on the discretion of ICJ

The International Court of Justice (ICJ) does not determine the UN's legal status. The UN's legal personality is inherent and recognized under international law. This option is incorrect.