单选题
13.He asked me to lend him some money, which I agreed to do, ______that he paid me back the following week.
【正确答案】
C
【答案解析】句中which引导非限制性定语从句，on occasion表示“偶尔间断地，不时地”；onpurpose指“故意地，为了，特地”；on condition后常跟that从句，表示“条件是”；only if则指“只有当……时才，只有当”。可见，C项符合题意，为正确答案。