The passive voice (be + past participle) isoften used in polite speech when a personwants to avoid mentioning the subject. For example, instead of saying "Kevin made amistake" (active voice), one could simply say"a mistake was made" (passive voice).
当说话者想要避免提及动作的主语的时候，使用被动语态（be + 过去分词）会显得比较礼貌。比如，与其使用主动语态说“Kevin madea mistake (Kevin犯了个错误)”，不如直接用被动语态说“a mistake was made (出现了一个错误)”。
To make a passive sentence, we replace the subject (Kevin) with the object (a mistake) and add "be + past participle" (was made.) "Amistake was made." As you can see, the passive sounds more polite because we avoid saying who caused this problem. This structure is very common at work and incustomer service.
想造一个被动语态的句子，我们可以把主语（Kevin）替换成宾语（a mistake），然后加上“be + 过去分词” (was made.) 就成了“Amistake was made.” 可以发现，被动语态听起来要更加礼貌，因为我们避免了提及是哪个人导致了问题发生。这个用法在工作中和客户服务中十分常见。
We can also combine the passive with other structures like "should have + been + pastparticiple" which is used to show regret. For example, in today"s lesson the speaker said, "You should have been informed."
我们还可以把被动语态和其他结构结合起来使用，比如“should have + been + pastparticiple (本应该...)”，这个结构用于表达遗憾。比如，在今天的课程中，说话者说到：“You should have been informed. (本应该提前告知您的。)”
Here is the pattern: Subject + should have + been + past participle.
结构为：主语 + should have + been + 过去分词。
They should have been told.他们本应该被告知的。
You should have been messaged earlier.本该早一点发消息给你的。
