Having followed several Moodle community and other links, I've found this procedure to be perfectly successful in Moodle 2.5: (This procedure essentially uses an external tool for consistent, complete TeX conversion throughout the multi-choice question)
- Site Admin→Plugins→Filters→Manage filters→[disable TeX notation]
- Site Admin→Appearance→Additional HTML→[add the following to the "Within HEAD" field]
- <script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"> </script>
- Consider installing and pointing Additional HTML HEAD to your own copy of MathJax if you control the server
Output (touchable answer choices with randomly-determined 'seed' number)
Samples of code used to produce output