解析:It为形式主语,无实际意义。was great为系表结构,作谓语。of him为不定式的逻辑主语。能与介词of搭配的形容词一般用来评价人的品德、性格特质等。to develop...为动词不定式短语,是句子真正的主语。
2. It was difficult for her to do that kind of work back in those days.
句型结构:It+be+adj. + sb+to do sth
解析:It为形式主语,无实际意义。was difficult为系表结构,作谓语。for her为不定式的逻辑主语。与介词for搭配的形容词一般用来描述事物的特征。to do that kind of work为不定式短语,是句子真正的主语。
3. It was amazing that he did scientific research in physics and chemistry even though he didn't receive a formal education.
句型结构:It+be+adj. + 从句
解析:It为形式主语,无实际意义。was amazing为系表结构,作谓语。that he did scientific research...是that引导的主语从句,是句子真正的主语。

第1个空答案：for
第2个空答案：that引导的主语

【解析】
1. 分析第二个句子的结构，结合给出的解析说明句中使用了介词for引出不定式的逻辑主语sb，对应句型It+be+adj.+____ sb+to do sth，可得出第一个空的答案为for。
2. 分析第三个句子的结构，结合给出的解析说明句中真正的主语是that引导的主语从句，对应句型It+be+adj.+____ 从句，可得出第二个空的答案为that引导的主语。
【答案】
for；that引导的主语
【知识点】
形式主语句型
It固定结构
主语从句
【点评】
本题考查it作形式主语的两类高频固定句型，结合配套的句子解析提示即可完成填空，重点区分it作形式主语时指代不定式和指代主语从句的不同结构差异，帮助学生梳理相关基础语法框架。
【难度系数】
0.7

一 用of、for或that完成下列句子
1. It was admirable he kept doing scientific research all his life.
2. It was brave the soldiers to protect the dynasty from its enemies.
3. It's important people to help each other during tough times.
4. It is creative chemists to use colours to teach children about science.
5. It was amazing researchers made great discoveries in just a few months.
6. It is necessary young people to explore widely to find their true dreams.
7. It was wise the designers to learn from both the East and the West.
8. It was truly inspiring his dream to control the disease finally came true.
9. It's amazing every corner of the town tells a story from the past.
10. Thanks to the high-speed railway, it's convenient us to travel around.

1. that
2. of
3. for
4. of
5. that
6. for
7. of
8. that
9. that
10. for

本题考查it作形式主语的三类固定结构用法，符合九年级所学的主语从句和固定句型知识点：
1. 若空格后是结构完整的陈述句，需要用that引导主语从句，构成"It is/was + 形容词 + that从句"结构，it是形式主语，that引导的从句是真正的主语。
2. 若句中形容词是描述人物本身品格、特质的词汇（如brave、creative、wise等），后接sb. to do sth.结构时，搭配介词of，构成"It is/was + 描述人物品质的形容词 + of sb. to do sth."结构。
3. 若句中形容词是描述行为/事件的性质、属性的词汇（如important、necessary、convenient等），后接sb. to do sth.结构时，搭配介词for，构成"It is/was + 描述事件属性的形容词 + for sb. to do sth."结构。
结合每个句子的结构特征和形容词属性即可确定正确答案。