WebForm module: Conditionally hide "File Upload"?

Using the WebForm module we have created a page with (among other things) a “File Upload” field and a “Select Options” (Radio Buttons) field. How do we hide the “File Upload” field based on the “Select Options” selection?

For example, let’s say the radio buttons have labels A, B, C, D, and E.

  • If radio button D is selected, we want them to be able to upload a file.
  • If any other radio button or no radio button is selected, the upload file field is hidden

Alternately, if they specify a file, can the “Select Options” automatically be forced to “D”?

Drupal version: 

Source: https://www.drupal.org/taxonomy/term/22/feed