it's C becasue the client would not appreciate the publicity of what they are buying from the establishment. they dont want to be rushed of feel like you are not professional enough to answer their questions.
Explanation: If you want to influence a customer positively, talking in a hurried manner is not a good option, because it is not comfortable for anyone.
Answering the queries briefly may also not be a good option, because maybe the customer feels that you don't want to spend your time with it.
Wearing casual attire may seem "unprofessional" for someones, so this also may be discarded.
The correct option is C, being confidential with the customer will give him a lot of confidence with you.
