答案：
1. was invented
2. are connected
3. was introduced
4. was pressed
5. was found
解析（都是被动语态）：
1. in 1876 过去时，单数 → was invented
2. people 复数，一般现在时 → are connected
3. in 1920 过去时，单数名词 → was introduced
4. wasn’t 提示一般过去时，button单数 → was pressed
5. 轮子被发现，过去时，单数 → was found
句子中文翻译:
1. The telephone was invented by Alexander Bell in 1876.
电话是亚历山大·贝尔在1876年发明的。
2. People all over the world are connected to each other through the internet.
全世界的人们通过互联网彼此联系在一起。
3. The word “robot” was introduced for the first time in a play in 1920.
“机器人”这个单词于1920年在一部戏剧中首次被提出。
4. It wasn’t supposed to make such a loud noise when the button was pressed to start the machine.
按下按钮启动机器时，本不该发出这么大的声响。
5. It is believed that the world’s oldest wheel was found in Eastern Europe.
人们认为，世界上最古老的轮子是在东欧被发现的。
学习短语：be supposed to do / be sth.
翻译：应当做（某事）；应当是（某物）
结构拆解
1. be supposed to do sth. → 应当/应该做某事
例：You are supposed to arrive on time.
你应该准时到达。
2. be supposed to be sth. → 应当是/理应是……
例：This is supposed to be a secret.
这本该是一个秘密。
重点讲解：
- 这个短语的语气常用来指：按规则、习俗、常理应该……
- be动词随人称、时态变化（am / is / are / was / were supposed to…）
- 否定形式：be not supposed to do 不应该、不准（常用来表示禁止）
例：You aren’t supposed to smoke here. 这里不允许吸烟。
