Step 1: Understand the word.
The word requisite means something that is necessary or required.
Step 2: Analyze the options.
Dispensable means something that can be done without, i.e., not necessary. This is the exact opposite.
Random means without order, unrelated.
Inappropriate means not suitable, not opposite.
Chaotic means disordered, unrelated.
Step 3: Conclusion.
Thus, the correct answer is Dispensable.