Final answer:
Without the survey results data, we cannot determine the most frequent choice of favorite coffee drink flavor from the options provided.
Step-by-step explanation:
To determine the most frequent choice of favorite flavor of a coffee drink from the survey, we would need the data from the survey results showing how many people chose each option (C = Caramel, H = Hazelnut, M = Mocha, P = Plain, V = Vanilla). Since the survey results are not provided, we cannot accurately identify which flavor was most preferred. Typically, this would be a simple matter of counting the number of responses for each flavor and identifying which has the highest count. However, as specific data is not included in the question, it is impossible to determine the correct answer from options a. Mocha, b. Hazelnut, c. Vanilla, d. Plain.