把下面两个句子合并成含有定语从句的主从复合句（每空一词）
He has lost his new bike. His new bike cost him 1800 yuan.
He has lost his new bike ____ ____ him 1800 yuan.
答案
which,cost
知识点：定语从句
合并后主句部分来自第一句，定语从句部分来自第二句。合并后的先行词是his new bike，指物，且关系词在定语从句中作主语，所以关系词要用关系代词which或that。故从句部分为“which/that cost him 1800 yuan”，放在先行词his new bike后边。合并后的完整句子为“He has lost his new bike which/that cost him 1800 yuan.”。故答案为which cost或that cost。
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