This is a LaTeX error from your LaTeX document. If it is related to the use of the automultiplechoice package, please try to make a minimal example where this error shows, and post the tex file. If not, you can also post your question on a generalist LaTeX-related forum or Q&A.

ok thanks.
sigskip \signature{\textarab{رئيس القسم}}{\textarab{د.عبد الله الصبحي \\ مدير المدرسة }} i put "\textarab" inside "\signature", but after i delete "\textarab" , the treatment process to continue indefinitely. it was forced to restart the computer.

i got the problem. the problem her:

 \sigskip \signature{\textarab{رئيس القسم}}{\textarab{د.عبد الله الصبحي \\ مدير المدرسة }}

Sorry, I mean a complete minimal example, that is a latex file that you can compile directly to see the errors you are describing, though as small as possible so that the errors can be understood with not so much pain.