When setting up WEB voting for your poll you can choose to indicate the correct option in the results page of the widget.
Scroll to the "Results" section and change:
"Correct Option Enabled" to "ON"
the "Correct Option" to the desired option from the drop-down list
and switch "Show Correct Option on Results" to "ON" (is set to "OFF" by default)
Note: this feature may not be available for some of the web templates. Availability may change without notice.