First Principles Thinking: US GAAP pension components
B is correct. Under US GAAP, the CFA Curriculum states that the change in net pension asset or liability each period is viewed as having five components: (1) service costs, (2) interest expense, (3) expected return on plan assets, (4) past service costs, and (5) actuarial gains and losses.
A is incorrect because three is the number of components under IFRS, not US GAAP.
B is incorrect because there are five, not four, components under US GAAP.