Under IAS 19, Employee Benefits, the following disclosures related to the defined benefit obligation would typically be required:

B. Significant actuarial assumptions used to determine the present value of the defined benefit obligation

Therefore, option B is the correct disclosure requirement under IAS 19. Disclosing the current and non-current defined benefit obligation and disaggregating the present value of the defined benefit obligation by employee age would provide additional relevant information but are not directly mandated by IAS 19. However, it is important to note that while IAS 19 does not explicitly require a breakdown of the obligation by employee age, it does emphasize the need to disclose the significant actuarial assumptions used in calculating the present value of the defined benefit obligation, which can significantly impact the reported amount.