What Is Interest Rate Immunization in the Context of Bank

What is interest rate immunization in the context of bank gap management?

A) the strategy of holding more interest rate sensitive assets than interest rate sensitive liabilities
B) the strategy of holding fewer interest rate sensitive assets than interest rate sensitive liabilities
C) reducing the size of the balance sheet
D) structuring a bank's portfolio so that its net interest revenue and/or the market value of its portfolio will not be adversely affected by changes in interest rates