The COLLES and ATTLS surveys are standard and ship with Moodle; they cannot be edited through the Moodle interface. They are well put-together with appropriate labels, and generally screen reader users had no trouble.
The survey offers six choices to users. Five of these choices have column heading and labels; the sixth has only a label, "Default." "Default" is not an acceptable answer for any question. The survey will refuse to submit if any question is answered with "Default."
Why it matters
Sighted users don't see the "Default" label, they see that this column of radio buttons doesn't have a heading and thus appears not to be an available choice. Screen reader users do not see the headings at all times, relying instead on the labels. Some did not understand what "Default" meant, and others thought it was a valid choice.
The price of confusion for screen reader users is high: after completing the survey, leaving a few questions as "Default," they tried to submit and received an error. They had to read back through each question and its answers, searching for ones answered "Default."
First, a note should be made at the beginning of the survey that all questions are required and must be answered. Second, the "Default" choice should be removed, and the middle option ("Sometimes") selected by default instead.
Certainly there are arguments against this approach, but I can't think of a label for the "Default" option which makes sense in this context. More design and testing is needed.