1 Why did you have to go to school last Saturday
2 You shouldn't spend too much time playing games
3 The children must wear a uniform
4 You should say sorry to your parents
5 You shouldn't drink so much coffee
6 He doesn't have to apologize. He was absolutely right
7 We have to give him our answer today or we'll lose out on the contract
8 You should go and lie down
9 You don't have to learn all the new words
10 Do you have to attend every English lesson
11 Harry should take a holiday
12 You shouldn't leave a child unsupervised
13 You have to register in advance to take the course
14 You don't have to read all those books
15 You should spend more time with her

What is Air Pollution?
Air pollution is a major change in air composition, caused by smoke, dust, water vapor or strange gases entering the air, causing strange odors, reduced visibility and climate change. They directly affect the health of humans as well as animals and plants on earth.
Current status of air pollution in Vietnam
Air pollution is a serious problem in the world and Vietnam is no exception. According to the annual report on the environmental performance index (EPI) conducted by the US Environmental Organization, Vietnam is one of the 10 countries with the highest air pollution levels in Asia.
 Current status of air pollution in the world
According to the 2020 State of the Global Air Report released by the Health Effects Institute (HEI) and the Institute for Health Metrics and Evaluation (IHME) at the University of Washington and the University of British Columbia on October 21, Air pollution in the world is very alarming. 
Air pollution is threatening human life 
The causes of air pollution come from many sources, there are basically two main causes: man-made and natural.
Natural causes
There are many natural causes such as volcanic eruptions, tsunamis, etc. that also pollute the air
Causes from humans (man-made)
There are many man-made causes from daily activities and agricultural production activities. Not only Vietnam but many developing countries are also experiencing this situation. Smoke and dust from exhaust pipes of factories and plants in industrial zones darken the sky. They emit CO2, CO, SO2, NOx and some other organic substances at extremely high concentrations.

1. We stayed with a host family.
2. I went on day trips.
3. They visited water parks.
4. I saw local attractions.
5. We went on a cycling tour.
6. They travelled by train.
7. They went on cultural visits.
8. We visited museums and galleries.

1. We stayed with a host family.
2. I went on day trips.
3. They visited water parks.
4. I saw local attractions.
5. We went on a cycling tour.
6. They travelled by train.
7. They went on cultural visits.
8. We visited museums and galleries

In recent years, the increasing celebration of festivals such as Christmas and Halloween among young Vietnamese people has sparked a debate on cultural influence. While some view this trend as harmless, others express concern about the potential erosion of traditional values. 

In my opinion, celebrating these festivals can be beneficial for several reasons. Firstly, it promotes cultural exchange and broadens horizons. Embracing different traditions allows young people to become more open-minded and globally aware. This can foster a more inclusive society where diversity is appreciated rather than feared. 

Secondly, these celebrations provide opportunities for socializing and community building. Festivals like Christmas and Halloween bring people together, creating joyful and memorable experiences. They offer a break from routine and can enhance the sense of belonging among young people, especially in urban areas where traditional community ties might be weaker.

However, it is crucial to balance this with the preservation of Vietnamese traditions. Promoting traditional festivals and cultural education can ensure that young people remain connected to their roots while enjoying the benefits of global cultural exposure. In conclusion, the celebration of foreign festivals should be seen as an enriching addition to, rather than a replacement for, Vietnamese culture.

I visit our uncle's house not only in spring but also in autummn.

I visit our uncle's house not only in sping but also in autumn 

In the study of events in Vietnam and throughout world history, we examine the past and present.

We study events in the past and present in Vietnam and throughout the world in history