All but one ________ here just now．
A.isB.wasC.has beenD.were在线课程D
主语的附属说明部分不能算主语，如the student with a teacher，that boy together with two women，all but one，其中with a teacher，together with two women，but one都属主语的附属说明部分，因此该题最佳答案为D。