Step 1: Understanding the Question:
We must state the purpose of the oblique aerial perspective in Sahibdin's Yuddha Kanda of the Ramayana.
Step 2: Check the options:
Decoration, Mughal influence and showing the scale of war are not accepted by the NTA key.
Step 3: Option 4:
The oblique aerial view lets the painter place many figures and events in one scene. This is called narrative density, and the key marks it correct.
Final Answer:
The correct option is 4 (narrative density), as per the NTA final answer key. \[ \boxed{\text{Employ narrative density.}} \]