Articulate storyline: How to navigate through the NVDA player for graded questions from a question bank?

I am working on making inbuilt storyline question bank questions accessibility compliant.

 

I have attached a sample screenshot for example. After fixing the focus order and alt text for this question,  I used down arrow to go to a certain option. However I am unable to select an option and submit using the keyboard and NVDA player. What keys must I press to navigate and submit a right answer whilst using NVDA?

 

I need suggestions for accessibility for articulate storyline's graded questions