Answer:
a. reaction
Step-by-step explanation:
Participant reactions are the most basic way to see how they assessed the training and development evaluation made by the HR department. Although the behavioral change would fully reflect how the development and training actually went, it takes time to see when and how employees will implement the learnt skill or knowledge in work.
Therefore, the easiest and least expensive way to measure satisfaction and get timely feedback is to follow the reactions of the participants.