This is a display issue caused by the way Moodle force-centres media players for files embedded in the question text of the sub-questions. The players will typically take up the whole width of the space and the answer option drop-downs are pushed off the right hand side.
See attached screenshot. In the pictured example the student must listen to the embedded sound file and then choose from the drop-down what they are listening to. Only they can't get to the drop-down.
This is still the case in the Moodle QA site, current version.