You can create a Tex Open MC question from a blank TeX Open question type (obtained by following the instructions here) by including the following:
\choice{}{1}{Here is choice one.}
\choice{}{2}{You set the text yourself.}
\choice{}{3}{Even equations can go in here.}
"ans1 = 1;" indicates that the first choice is the correct answer.
Click here for more information about the code portion.