Keywords: OCS, registration form fields, add, remove, required
必須修改程式，才能新增、移除註冊報名表的某些欄位，或將某些欄位設為必填。
You can do this, but you'll have to edit the underlying codebase yourself. There are a fair number of threads on the forum about adding/removing form fields, and also about making fields required -- just search using those as keywords.