Tested in Firefox 59.0.2:
After submitting an incorrect reply in the prelab and replying again, an additional checkbox column is displayed.
All checkboxes mapped to the same reply have the same id and name, e.g. mcCheckMark_q27_a0
The label maps to all those checkboxes (as their id is identical): ''
When clicking on the label if more than one reply checkbox is displayed for one answer, nothing happens, as (I suspect) Firefox is unable to create a unique mapping between input and label.
Furthermore, all id's have to be unique within a document (https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/id).
This could be resolved by generating unique ids, e.g. mcCheckMark_q27_a0_0 for the first checkbox and so on.
Example ([ ] is a checkbox, [d] means disabled checkbox):
On second thought, the browser will try to toggle the state of the first checkbox it finds.
As this is disabled, nothing happens when clicking the label.
Tested in Firefox 59.0.2: After submitting an incorrect reply in the prelab and replying again, an additional checkbox column is displayed. All checkboxes mapped to the same reply have the same id and name, e.g. mcCheckMark_q27_a0 The label maps to all those checkboxes (as their id is identical): ''
When clicking on the label if more than one reply checkbox is displayed for one answer, nothing happens, as (I suspect) Firefox is unable to create a unique mapping between input and label. Furthermore, all id's have to be unique within a document (https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/id).
This could be resolved by generating unique ids, e.g. mcCheckMark_q27_a0_0 for the first checkbox and so on.
Example ([ ] is a checkbox, [d] means disabled checkbox):
Question [d] [ ] Reply Option 1 [d] [ ] Reply Option 2
On second thought, the browser will try to toggle the state of the first checkbox it finds. As this is disabled, nothing happens when clicking the label.