Explanation

An interest rate swap can be replicated using a pair of bonds:

• Long a fixed-rate bond and short a floating-rate bond (from the perspective of the fixed-rate payer)
• Short a fixed-rate bond and long a floating-rate bond (from the perspective of the fixed-rate receiver)

This replication method is the easiest because:

1. Direct cash flow matching: The fixed payments from the swap match the coupon payments from the fixed-rate bond, while the floating payments match the floating-rate bond payments

2. Simplicity: Only two instruments are needed, making it straightforward to implement

3. Standard valuation: Bond pricing formulas are well-established and easy to apply

4. No complex derivatives: Unlike options or futures, bonds are simpler instruments with more transparent pricing

Option B (portfolio of interest rate options) and Option C (portfolio of interest rate futures) are more complex and require multiple positions to replicate the swap's cash flows accurately.