What exactly does focal loss down-weight?

For a correctly classified example with target-class probability ptp_t close to one, what is the primary effect of the focal-loss factor (1−pt)γ(1-p_t)^\gamma with γ>0\gamma > 0?

A

It assigns the example a larger class-balancing coefficient regardless of α\alpha

B

It reduces that easy example's contribution relative to difficult examples

C

It increases its gradient so that confidence approaches one more quickly

D

It converts cross-entropy into a margin-ranking objective