Answer
a. observation ( O )
b. hypothesis ( H )
c. experiment ( E )
Work Step by Step
a. Observation, as it is observed on a daily basis, but there are not any concrete proofs for it.
b. As the person is assuming that if he will stop drinking coffee in the afternoon he will get sleep at night, hence it is the hypothesis.
c. Since the person is doing the practical experience of drinking coffee only in the morning, it is an experiment.
