Another place to look: whoever made that quiz question - if they "copy and pasted" the answer text into those Choices text boxes, there there could be some extra code that got pasted in.
If you edit that question question and go down to each answer, click the HTML button for each answer -- see if there is some extra code in there that can be cleaned out. In the example below, the "br" tag is not necessary and adds an unintended line break. On the other hand, in the example below, the "p" tags are not necessary either, but as long as they present consistently in all choices for that question, then it's fine to leave. I guess the point is to see what is different between the answer choices that might be causing that issue. If all answer choices are consistent, then the issue is coming from elsewhere and Tim's recommendation will help pin point that.
But as Tim stated, if this were the case, it should show up in both the preview and the attempt, but worth a check i guess...