Often the final punctuation of a paragraph gets separated from the text and unnaturally appears on its own line. This doesn’t look right. It isn’t very important for language learning, but creates a bad impression of the lesson text.
The problem is caused by the lesson markup: every word is wrapped in a element and the browser treats the closing tag as a potential line break.
The solution is to add an additional inline element around every followed by punctuation AND the punctuation and make sure the outer element has the style white-space: nowrap applied.