Frame around knowledge check questions

Hi all, 

I am currently creating a course in Rise. I am using the "Knowledge Check" element. This automatically puts a fine thin line around the element. Is it possible to turn off this line? In this article under point 3, for example, a knowledge check is shown that does not have a frame: https://community.articulate.com/series/allison-s-articles/articles/7-creative-ways-to-use-images-in-rise-360-courses

Best, 
Laura