In order to monitor the audience reaction on multiple call to action in the creative, you can add engagement trackers from Canvas. 

To add engagement tracker from Canvas

  1. Open the creative in Canvas.
  2. Select the asset, on the Events pane, select the Click/Tap event to select Fire Custom Tracker action to provide the tracker. 

Fire Custom Tracker

  1. Click Add.

Similarly, you can add multiple custom trackers on the creative from the Canvas.

The following link displays the list of actions that you can associate with the events.

Action List in Canvas