Thank you for asking this question, I just learned something!
I did not know the answer, so I went to look at the code (question/format/gift/format.php), and the answer is much more interesting than I expected.
By default, it is Moodle auto-format, however, you can write something like
[html]<p>Here is some HTML question text</p>
That is, with the format you want in square brackets. The format names recognised are moodle, html, plain and markdown.
Quiz
What is the default text format for GIFT?
A vitát lezárták, már nem szólhat hozzá.