Here are the completed sentences using the provided words:

### E3
**Question 1:** We should **appreciate** the beauty of nature and protect **it** for future generations.
**Question 2:** Pollution from factories can **affect** wildlife and ecosystems, **harming** the environment in negative ways.
**Question 3:** It is important to **preserve** natural habitats so wildlife will be safe.
**Question 4:** The Moon takes about 27 days to **orbit** the Earth.
**Question 5:** Human activities like deforestation can **affect** the environment negatively.
**Question 6:** Factories should not **release** harmful chemicals into the air or water.
**Question 7:** Scientists **observe** the stars to learn more about the universe.

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### E4
**Question 1:** The documentary about marine life was truly **fascinating**.
**Question 2:** Animal **droppings** can be used as a natural **fertilizer** for farming.
**Question 3:** Water is **essential** for all living organisms to survive.
**Question 4:** Pollution is a major **threat** to the health of our oceans.
**Question 5:** The North **Pole** is one of the coldest places on Earth.

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### E5
**Question 1:** Lakes, rivers, and oceans are examples of **water bodies**.
**Question 2:** The Sun and the planets around it form our **solar system**.
**Question 3:** The Amazon rainforest is home to diverse **flora and fauna**.
**Question 4:** Earth is the only known planet to have **liquid water**.
**Question 5:** Mountains, valleys, and plains are different types of **landforms**.
**Question 6:** Astronauts explore **outer space** to learn more about the universe.

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### E6
**Question 1:** The Arctic and the Antarctic are known as the Earth's **poles**.
**Question 2:** A **grassland** is a large open area covered with grass, often found in Africa and North America.
**Question 3:** Tigers, elephants, and rare plants are protected in **nature reserves** for wildlife.
**Question 4:** Plants and animals living in different environments are part of the Earth's **food chain**.
**Question 5:** Lions hunt zebras, and zebras eat grass. This is an example of a **food chain**.
**Question 6:** Forests, deserts, and oceans are different types of **habitats**.

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