Which of the Following Is an Example of Informal Training

Which of the following is an example of informal training?

A) A worker chooses to take a course at a local community college.
B) An employer requires all workers to take an on-line course.
C) Over lunch,a senior employee explains a difficult concept to a new worker.
D) Through experience,a worker learns a more efficient way to do his job.
E) The supervisor schedules a meeting with a worker to discuss better ways to perform a job.