Validate questionnaire options

[jsorva]

Sometimes one edits a multiple-choice question, adding, reordering, and changing the options. One carelessly writes something like this pick-any question:

Question text. Here are the options:

c.  option 1    
*d. option 2    
*e. option 3    
*f. option 4    
e.  option 5    
*f. option 6

Note that the options are not properly labeled from a to f, and there are duplicate labels.

It has happened a couple of times that something like that has ended up in production. The symptoms for students are really weird and confusing.

It should be pretty straightforward to check for duplicate labels and, perhaps, to enforce labeling from a upwards.