第11题: [单项选择]It has been quite a long time ______ the two companies established a business relationship. A. although B. because C. if D. since 参考答案:A 答案解析:[解析] 本题考查连词辨析。since引导的从句,可表示“自从……以来”,其主句用完成时态.从句用一般过去时。例如:Since he entered the university,he has mad