"that is written in pencil"就是指的a letter is written in pencil.that =a letter那letter 不就是 write 的宾语了吗这里是被动语态。主语是that也就是letter。被动语态和我要弄懂的东西没有联系啊是？ 我觉得如果我说letter是宾语 那这句话就没主语了 能这样理解吗不然我实在弄不清这句是 同位语从句。a letter is difficilt to read 是主句。that is written in pencil 是插入句。是对a letter的修饰。如果letter 做宾语，句子就要改为 somebody writes a letter in pencil. the letter is difficult to read .前者letter就是宾语。恩有道理 谢谢~~~~