1. I , who am you friend, will help you certainly.
学习者受疑问句Who is that man? Who is coming? 等的影响，在定语从句中也用is，忘记了先行词是I，后面的动词应为am。
2. He is one of the teachers who know French in our school.
在定语从句的习惯使用中，one of后面的名词是复数，这个复数名词制约后面的定语从句的谓语动词，因而know不作加s. 而在one of 前面有the或 the only时，后面引导的定语从句中的谓语动词则用单数形式。如：
3. He is the only one of the teachers who knows French in our school.
而在现代英语中我们也可以见到在one of 加名词复数的后面定语从句作单数动词的情况：
4. This is one of those novels which begins with an idea.
然而在测试中我们还是按习惯用复数动词为宜。
