观察下面的句子, 研究句中黑体词在句中的功能:
1. The time when I first met Nelson Mandela was a very difficult period of my life. __________________
2. He was generous with his time, for which I was grateful. __________________
答案: 1. when为关系词, 引导定语从句, 修饰先行词the time, 且在从句中作时间状语。
2. which为关系词, 从句修饰整个主句, which在从句中作介词for的宾语。
