One form of delegated legislation is statutory instruments.
Statutory instruments are rules, regulations, and orders made by government ministers, departments, and other bodies under the authority of an Act of Parliament. In other words, statutory instruments are laws made by bodies other than Parliament but with the authority of Parliament.
Delegated legislation refers to the process of entrusting some of the law-making powers of the legislature to the executive or other subordinate bodies. This form of legislation is necessary to enable effective governance and to ensure that laws can be made and amended quickly and efficiently in response to changing circumstances.
Therefore, of the four options given, statutory instruments are a type of delegated legislation, while case laws, conventions, and man-made laws are not forms of delegated legislation.