since与for引导的时间状语 — 英语词汇题
题目
用 since 或 for 填空，每空一词：1. We have known each other ______ we were in primary school. 2. My grandparents have lived in the new flat ______ about ten years. 3. He has kept the stamp ______ 2015. 4. The factory has produced bikes ______ three months.