It is ... (when/where/because) that ... (the use of the emphatic it: 用于强调句的it)e.g.It was while I was scanning listings from our real estate agent that I first learned of it. (Para. 3)It was in the small town of Yucca that the Zeuschels found the house they wanted.It was because there was an accident on the road that we were late.It was Sam who/that called the police for help.1 they, the day before yesterday, set out____2 by the roadside, find, the lost wallet, I____3 until, get everything ready, he, for the experiment, leave, the lab, Xiao Wang____

我们来逐题分析并完成这三个强调句。题目要求使用 强调句型 “It is/was ... that ...” 结构，这是英语中常见的强调句型，用于突出句子中的某一部分（如主语、宾语、时间、地点、原因等）。

强调句的基本结构是：

> It is/was + 被强调部分 + that/who + 其他成分

注意：

• 强调人时可以用 who 或 that，其他情况一般用 that。
• 原句必须是一个完整句子，我们从中提取要强调的部分放入“It was...that...”结构中。
• 强调句中不能出现 when, where, because 等连接词作为 that 的替代（除非原句就是强调时间/地点/原因，但要用 it was ... that ...，而不是 it was ... when ... 这种结构，除非是状语从句的其他结构，但这里题目明确说是强调句）。

我们逐题来解：

第1题：they, the day before yesterday, set out

原句应该是：They set out the day before yesterday.
（他们前天出发了。）

我们可以强调不同成分：

• 强调主语：It was they who/that set out the day before yesterday.
• 强调时间：It was the day before yesterday that they set out.

题目没有指定强调什么，但根据给出的词语顺序 “they, the day before yesterday, set out”，可能倾向于强调 they 或 the day before yesterday。

但通常在练习中，如果时间状语单独列出，往往是强调时间。

不过我们看词语顺序：“they, the day before yesterday, set out” —— 这像是主谓宾+时间，所以我们可以选择强调 时间 更自然。

✅ 正确强调句（强调时间）：
> It was the day before yesterday that they set out.

解释：我们强调的是“出发的时间”是“前天”。

第2题：by the roadside, find, the lost wallet, I

原句应为：I found the lost wallet by the roadside.
（我在路边找到了那个丢失的钱包。）

可以强调：

• 主语：I
• 地点：by the roadside
• 宾语：the lost wallet

题目中把“by the roadside”放在前面，可能是提示强调地点。

所以强调地点“by the roadside”：

✅ 正确强调句：
> It was by the roadside that I found the lost wallet.

解释：强调“找到钱包的地点”是在路边。

第3题：until, get everything ready, he, for the experiment, leave, the lab, Xiao Wang

这个句子结构较复杂，含有 not...until... 结构。

原句应为：
Xiao Wang did not leave the lab until he got everything ready for the experiment.
（小王直到为实验准备好一切才离开实验室。）

现在要使用强调句型强调 until... 这个时间状语从句。

注意：强调 not until... 结构时，需要用特殊结构：
> It was not until + 被强调部分 + that + 主语 + 谓语（用肯定式）

例如：

• It was not until midnight that he came back.

所以本题强调 “until he got everything ready for the experiment” 这个时间点。

✅ 正确强调句：
> It was not until he got everything ready for the experiment that Xiao Wang left the lab.

解释：强调“小王离开实验室”的时间是“直到他为实验准备好一切的时候”。

最终答案整理：

1. It was the day before yesterday that they set out.
2. It was by the roadside that I found the lost wallet.
3. It was not until he got everything ready for the experiment that Xiao Wang left the lab.

✅ 答案：

1. \boxed{It\ was\ the\ day\ before\ yesterday\ that\ they\ set\ out.}

2. \boxed{It\ was\ by\ the\ roadside\ that\ I\ found\ the\ lost\ wallet.}

3. \boxed{It\ was\ not\ until\ he\ got\ everything\ ready\ for\ the\ experiment\ that\ Xiao\ Wang\ left\ the\ lab.}