回複：再請8老師，我今年三月十五號畢業，現已遞交申請OP丅簽證，同時4月1號申請HB1，

Read these links:
http://internationalcenter.umich.edu/immig/fvisa/fj_travelpostopt.html
http://www.murthy.com/2012/12/07/f-1-students-be-prepared-while-traveling-on-opt/
http://www.ice.gov/sevis/travel/faq_f2.htm