Respuesta :
Answer: a. observing
Explanation:
Observation in research can be define as the visual examination of the outcomes of the experimental procedures or examination of naturally occurring process. This is important for framing the results of the experiment. The observation is particularly recorded in written notes, and photographs.
According to the situation given, he missed the observation in the scientific investigation. He must posses the proof of his observation before proposing the conclusion to his classmates.