【求科普】Virginia Polytechnic Institute的入学要求

狂发Email的时候发现这么个学校，感觉好恐怖啊

Enrollment Qualifications:
All new graduate students must complete the GTA Workshop (GRAD 5004, 1cr.)
International students with a 26 or below on the Speaking subtest of the Internet-based TOEFL must take either the SPEAK or TEACH test offered during graduate orientation.
Students on graduate assistantships must be enrolled for a minimum of 12 credits.
A minimum GPA of 3.0 must be maintained both overall and for all coursework on the Plan of Study (minimum for any one course is C-).
Full time enrollment = minimum of 9 credit hours, maximum of 18 credit hours
Graduate assistants, fellowship and scholarship recipients minimum is 12 credit hours.

问题如下：
1、何谓GTA workshop，我没搜到解释。
2、那真的是IBT的口语要求？我真的没有一点把握。。。
3、一直没搞懂这些credit hours，神马least 60 credit hour？

求科普帝