Ask about the usage of the words do, in, is, does.at, on, etc. That is, what words are used under what circumstances.

It is the third person singular of do.

When used as a notional verb, the subject +do/does+ other

When used as an auxiliary verb, it is often used in interrogative sentences, mainly to strengthen the mood and play an emphasis role.

Is is a copula, which is mainly used for subject+copula+slogan.

exist

Prepositions are in ..., in ... place, during ..., in the state of ..., dressed in ... in the manner of ... ...

At home, in, in, in, in, somewhere, in a relationship.

Inside, new, in power, fashion

People in power, power and ways to achieve goals

I haven't seen him for years.

I haven't seen him for years.

Will you take part in this whist card game?

Would you like to take part in the Whistler Bridge Competition?

They are studying.

They are doing research.

exist

Prepositions in, to, to

Kip (the basic unit of currency in Laos)

Methylene (extremely unstable radioactive element)

sealed

Abbreviated temperature

Example: I'm good at it.

I'm good at this.

I watch TV until ten o'clock in the evening.

I watch TV at night until 10.

There is little profit in selling newspapers at present.

There is no profit in selling newspapers now.

exist

Prepositions are in, by, in, about and based on (one day).

Wear, move forward, indicating continuity.

Connect, be in working condition or use, happen, be on duty

Abbreviation Lake Ontario

Example: I will play in five minutes.

I will play in five minutes.

The doctor asked me to take these pills.

The doctor asked me to take these pills.

The strike has lasted for six weeks.

The strike has lasted for six weeks.