A study conducted by Dr. Reyes examines a group of college students and asks them to answer whether they exercised at least three times last week (yes or no) and to rate their mood in the last week (1: Not happy at all to 5: Very happy). Her results show that students who exercised in the last week also reported happier moods. Can Dr. Reyes make a causal inference from her study? Select the best explanation for the response.
a. Yes, Dr. Reyes' study meets all three of the causal criteria.
b. No, Dr. Reyes' study meets only two of the three causal criteria: covariance and temporal precedence.
c. No, Dr. Reyes' study meets only one of the three causal criteria: covariance.
d. No, Dr. Reyes' study meets only one of the three causal criteria: temporal precedence.