Short answer with line doesn't show up correctly in Boost.

Short answer question

xxxxxxxxxxxxxxxxx  _____________________ xxxxxxxxxxxxxxxxxx.

Shows up like this:

xxxxxxxxxxxxxxxxx  

_____________________

xxxxxxxxxxxxxxxxxx..

In theme Clean the issue doesn't occur, only in Boost.

Steps to reproduce:

1. Create a short answer question in a quiz.
2. In the question text enter 5 underscores ( _____ ) in the middle of the text.
3. Save changes and preview the question.

Expected result: The short answer input box is displayed inline with the text.

Actual result: The short answer input box is displayed on a separate line from the text.