Good manners certainly connect people to their 18 environment.
答案：(B) social
social environment（社會環境）表示良好禮儀能將人與其所處的社會環境連結起來，呼應後文 a community and the people in it（群體與其中的人）；rural／clinical／mental 均不符合此處語意。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
四個都是形容詞，都修飾得了 environment，中文一個一個讀都成立；mental（心理的）特別誘人，因為前面一直在講禮節帶來的感受。
看動詞與受詞的組合：connect people to their ______ environment（把人與他們的 ______ 環境連起來）。被連起來的是人與人，所以那個環境裡必須有別人在。下一句把答案講得更白：Respecting good manners shows a desire to actively engage with a community and the people in it（想主動與社群、以及社群裡的人往來），community 與 people 都指向 social。全篇第二句 Good manners make the social world easier to navigate 更是直接用過同一個字。
rural（鄉村的）與禮節無關，文章沒有城鄉的討論。clinical（臨床的、醫療的）用在醫學情境。mental（心理的）講的是一個人腦袋裡的狀態，但 connect people to 要求的是人與人之間的連結，不是人與自己內心的連結。
connect A to B（把 A 與 B 連起來）、social environment（社會環境、人際環境）、engage with（與……往來、投入）、community（社群）、navigate（順利穿行、應付）、mental（心理的）
Having good manners is more than just being nice. Good manners make the social world easier to navigate. They provide guidelines to 16 in times of uncertainty and reduce the chance of awkward exchanges. For example, knowing who is supposed to go first or have a seat keeps us from having to negotiate every time. A world 17 good manners would be confusing and potentially confrontational.
Good manners certainly connect people to their 18 environment. Respecting good manners shows a desire to actively engage with a community and the people in it. 19 to adopt good manners sets people apart.
We might forgive people who let their manners slip, but we'll feel more positive about and strongly connected to those who 20. Good manners are very important because they teach us the proper way to behave in society.