1.He is a student.其可以缩写为He's a student.如对he提问则为Who's a student?
此为be动词中is的使用，其中is后接的是名词单数，不可数名词等。S翻译为"是".再如：She's a clever girl.(她是一个聪明的女孩)
2.Jack's father is a worker.对于Jack's提问我们要用Whose father is a worker?此为s形式为物主代词使用，相当于my your等形容词性物主代词其后接名词。S翻译为''的''。再如The man is black is Lily's uncle.（穿黑衣服的男人是莉莉的叔叔）
3.They are teachers，aren't they?此为反义疑问句。从are我们可以判断出句子是复数形式。也就是teachers表示复数。S为名词复数的后缀。再如All roads lead to Rome.(条条大路通罗马)
4.He usually sees the white dog on his way to school.对the white dog提问应是What does he usually on his way to school?此为s在动词的一般现在时在第三人称后的使用，句子改为疑问句时用助动词，并且去掉动词后s形式。再如God helps those who help themselves.（天助自助者）
5.There's a lovely hat on my desk.本句是be但是形式is在there be句型中的使用，there's 后接不可数名词或者可数名词单数。要注意就近原则的使用。 .在加菲猫的经典语录中有这样一句话体现出there's的经典。Money is not everything. There’s MasterCard & Visa（钞票不是万能的, 有时还需要信用卡）。
6.He's a teacher of the school.two years ago.本句是s在动词一般过去时he was的缩写形式，表示主语以前的某种状态。对two years ago 提问When was he a teacher of the school?
7.He's been to Beijing for 3 times 此为s在动词的现在完成是的使用。He's been to是he has been to的缩写，表示曾经去过。对于for 3 times提问。How many times has he been to Beijing?