If your surveys are set-up to be published to TripAdvisor, you can respond to the guests both publicly on the TripAdvisor site and privately via email to the guest.
To publicly respond to a survey that was posted to TripAdvisor, follow the normal steps to respond to a review on a review channel, as described here.
To privately respond directly to the guest who filled the survey, follow the normal steps to respond to a survey, click here for instructions.
Note: If you first respond publicly on TripAdvisor and later privately via email to the guest, the public response will be available on the respective Review and can be seen on "All Reviews", the private response will be available on the respective Survey on "All Surveys".
If you first respond privately via email to the guest and later respond publicly on TripAdvisor, the public response will be available both on the respective review on "All Reviews" and the respective Survey on "All Surveys".