Which IBM Watson service should the IT helpdesk use to drive insights from the texts and to look for patterns among complains for improvements?

The IT helpdesk of a large enterprise routinely conducts surveys of its users. The survey allows the users to rate the performance of the helpdesk and to enter about 3-4 lines of comments in a free form text field.

Which IBM Watson service should the IT helpdesk use to drive insights from the texts and to look for patterns among complains for improvements?
A . Use Discovery to extract keywords and entities for common patterns across the comments plus gain insight into the sentiment expressed by each comment
B . Natural Language Classifier to evaluate sentiments expressed in the comments
C . Use Natural Language Classifier to look for concepts mentioned in the review
D . Use Personality Insights to analyze traits of the users logging the comments

Answer: D