Explanation:

- (1) Context: The Ministry of Defence is issuing a sanction letter for granting permanent commission to women officers.

- (2) Context: Addresses the purpose of the letter, which is to grant permanent commission.

- (3) Context: Indicates preparatory actions initiated by the Army Headquarters.

- (4) Context: The phrase implies a process waiting completion before scheduling a Selection Board for officers.

- (5) Context: Refers to the completion of necessary papers and forms by the officers.

- Option 1: Unnecessary: Means not needed or essential, which doesn't fit here as documentation is required.

- Option 2: Optional: Means not mandatory, which is not suitable since the context suggests documentation must be completed.

- Option 3: Gratuitous: Means uncalled for or unwarranted, which doesn't match as the documentation is necessary.

- Option 4: Requisite: ? Means necessary for a particular purpose, which fits the requirement of completing necessary documentation.