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.
New words：
emergency [ɪˈmɜrdʒənsi] n.突发事件；紧急情况；急诊
Sample Sentences：
We should keep calm in an emergency.
Call 120 at once if an emergency happens.
110 is the emergency call for police in China.
The doctor left quickly because of a medical emergency.
New words：
emerge /ɪˈmɜːrdʒ/ v.出现；浮现；显现；暴露；露出真相
同源联动记忆：
把emerge（v.出现） 和emergency（n.紧急情况） 绑定记忆
突然出现的（emerge）危险状况就是紧急情况（emergency），一次记两个词，效率翻倍。
必记高频搭配
emerge from...（从…… 中出现 / 浮现 / 走出）
The sun emerged from the clouds after the rain.
The children emerged from the forest and ran towards us.
The truth finally emerged after a long investigation.
investigation /ɪnˌvestɪˈɡeɪʃn/ n.调查；侦查；科学研究；学术研究
New words：
incident[ˈɪnsɪdənt] n.发生的事情；事变；事故；小事件
必记高频搭配
a funny/small/strange incident（一件有趣的 / 小小的 / 奇怪的事）
I still remember a strange incident that happened last summer.
an unexpected incident（一件意外的事）
An unexpected incident stopped us from going out for a picnic.
deal with an incident（处理一起事件）
The manager had to deal with the incident in the store.
historical incident（历史事件 / 事变）
This book tells us about many important historical incidents.
关键使用提醒
1.可数名词属性：incident 是可数名词，表达 “一件事” 用an incident，多件事用incidents，不能说 “a incident”（元音音素开头，用 an）。
2.语义范围：incident 的语义范围比 accident 广，所有 accident 都可以算 incident，但 incident 不一定是 accident。
3.写作加分：描述日常发生的小事时，用 incident 代替简单的 “thing”，让表达更精准，比如 “我经历了一件有趣的事”→ I experienced a funny incident.（比 I experienced a funny thing 更地道）。