A is correct

A. Cascading delete operations
Correct: When a record is deleted and there are child records associated with it, the cascading delete will trigger delete triggers on the child records. This is a typical scenario that causes triggers to fire.

B. Updates to Feed Items
Incorrect: Feed items, such as Chatter posts and comments, do not cause standard triggers to fire on the related object. While they can trigger other actions (like processes or flows), they do not invoke triggers directly on the associated records.