You are missing one column ..
as the instructions say:
3. Inside the third column, add just one thumbnail. Use "http://goo.gl/0Kd7UO" for the image.
So you need to add another div with the class
col-md-4 and inside that add a div with class
thumbnail and inside the thumbnail you will need to add the image..
col-md-4 needs to go after the closing tag of the second