在句①中，that引导同位语从句解释说明promise的内容，that不充当任何句子成分，只起连接作用。
而在句②中，that在其引导的定语从句中作动词visited的宾语，对先行词the chicken farm起修饰作用。
*名词性从句中，关于it作形式主语和形式宾语的易错点
1、名词性从句作主语或宾语时，为保持句子平衡，常用it作形式主语或形式宾语。
It’s a pity that he don’t come to give a speech.（形式主语）
We think it possible that you can finish the job today.（形式宾语）
2、谓语动词 appreciate, dislike, hate, like, love, make等接由if或when 引导的宾语从句时往往在从句前加上形式宾语it.
Eg: I would appreciate it if you could come to my birthday party.
3、动词hare, take, hide, punish, put等,后接由that 引导的病因从句式，往往在从句前加形式宾语it.
① I take it that you will be leaving Shanghai soon.
② we punished it that we had finished the project ahead of time.
4、短语动词answer for, count on depend on, insist on, see to等后接有that引导的宾语从句时，必须冠以形式宾语it.
① I’m counting on it that you will come.
② She’ll see to it that he goes ahead.
