Undergraduate employment recommendation form can't be written in preparatory class. According to the relevant public information, if you have completed the preparatory course, you can consider mentioning the relevant learning experience and achievements in your resume or cover letter, but it should not be listed in the undergraduate employment recommendation form. Preparatory classes do not belong to regular undergraduate education. If you have obtained a bachelor's degree, then the bachelor's degree will be the main education, and it will be more recognized by the employer in the job search process.