在英语语法中，强调句是一种非常重要的结构，它可以帮助我们突出句子中的某一部分信息。强调句的基本形式是“it is/was + 被强调部分+ who/that+ 其他部分”。通过以下练习，我们可以更好地掌握这种句型的应用。

练习一：改写句子

将下列句子改为强调句：

1. He went to the library yesterday.

- 改为：It was he who went to the library yesterday.

2. She speaks three languages fluently.

- 改为：It is she who speaks three languages fluently.

3. They met at the park last Sunday.

- 改为：It was at the park that they met last Sunday.

练习二：填空

用适当的词完成下列强调句：

1. It was ________ that I met my best friend after years.

- 答案：where

2. It was ________ that made me realize my mistake.

- 答案：what

3. It was ________ who helped me solve the problem.

- 答案：he/she

练习三：判断正误

判断下列句子是否为正确的强调句：

1. It was him who I saw at the party.

- 错误，应改为：It was he who I saw at the party.

2. It was because of the rain that we canceled the picnic.

- 正确，这是一个正确的强调句。

3. It was the book which I lost last week.

- 错误，应改为：It was the book that I lost last week.

通过以上练习，我们可以更加熟练地使用强调句来表达自己的意思。希望这些练习能帮助大家更好地理解和运用这一语法点。