New words：

investigate /ɪnˈvestɪɡeɪt/ v. 调查；侦查

词源联动：

由前缀in-（深入）+ 词根vestigate（追踪、探查）构成，和invest同根
核心均为 “投入精力去做某事”，invest 是 “投入钱 / 时间”，investigate是 “投入精力去探查、调查”，记同根关联更易掌握。

必记高频搭配

investigate sth（调查某事 / 某物）
The teacher will investigate the truth of the matter.

investigate into sth（深入调查某事）
Detectives are investigating into the theft in the shop.

investigate the cause of...（调查…… 的原因）
We need to investigate the cause of the fire.

关键使用提醒

1.及物 / 不及物搭配：

直接接 “事件、真相、原因” 等宾语时，不用加介词，✅ investigate the accident；表 “深入调查某事” 时，需加介词into，✅ investigate into the accident，不可混用。

2.同根词联动：

写作中可灵活切换investigate和investigation，让句式更丰富，避免重复，比如：
动词版：The police will investigate the fire cause.（警方将调查火灾原因。）
名词版：The police will start an investigation into the fire cause.

3.写作加分技巧：

描述正式场景的 “调查” 时，用investigate代替口语化的find out。
比如 “校方调查作弊事件”，不说 “The school finds out the cheating case”，说 “The school investigates the cheating case”，表达更正式、精准，贴合书面写作要求。

New words：

investor [ɪnˈvestər] n.投资者；投入者；投资机构
stock [stɒk] n.股票

Sample Sentences：

A wise investor never puts all money in one place.
The city attracts many foreign investors with good policies.
The investors had a meeting to talk about the stock market.

New words：

investment [ɪnˈvestmənt] n.投资；投入；投资额；投资物

必记高频搭配

make an investment (in sth)（在某事上进行投资 / 投入）
She decided to make an investment in her English learning.

investment in sth（对某物的投资 / 投入）
Our school’s investment in new books makes the library better.

investment of...的投资
Your investment of time in study will bring good grades.

New words：

invest [ɪnˈvest] v.投资；投入（时间 / 精力 / 心血）

核心语义围绕 “把钱 / 时间 / 精力投入到某事物中，以求回报” 展开。

必记高频搭配

We should invest more time in our English study.
You need to invest more time in practicing English.
Many people want to invest in the stock market for more income.

stock [stɒk] n.股票

New words：

submerge /səbˈmɜːrdʒ/ v.沉没；使…淹没；把…浸入；从视线中消失

Sample Sentences：

He submerged his hands in the cold water to cool down.
The diver submerged and looked for fish in the deep sea.