In this study we encountered with two main limitations. The first is that some students avoided answering to the questionnaire and a few of them just carelessly filled one column for all items of the questionnaire. It made us to exclude them from study. The second and paramount point is that since most of students were not well qualified in using English, we had to translate the questionnaire into the Persian language. Therefore, it is likely that the translated questionnaire may have not conveyed the items as clearly as the real questionnaire. However to hinder the latter limitation and to promote the reliability of the questionnaire we have revised the translation several times.