Rendering of cloze questions in pdf with r/exams

Question

I am trying to use r/exams to produce questions in pdf for a written exam. I would like that ##ANSWERn## in cloze questions is rendered in the pdf file, as follows:

1. a num question with a space:

   The unit price is ________. 
   

2. a schoice question with boxes:

   [  ] Yes    [  ] No
   

   or something similar.

However, it seems that ##ANSWERn## is not rendered at all in the pdf file and I couldn't find any documentation or example on how to change this.