D
Earth is the third planet from the sun. It is one of the four inner planets. The other three inner planets are Mercury, Venus, and Mars. The inner planets are also called the rocky planets, because they are made of rocks.
Earth is often called the “Water Planet”, because it is the only planet in our solar system which has liquid water on its surface. About 70% of the surface of Earth is covered by water! The other part of Earth is made up of continents and islands which have different landforms on them. Examples of landforms are mountains and plains. Plants and animals can live on Earth, because it has so much water.
Earth spins very quickly compared to other planets. It only takes Earth 24 hours to spin around its axis one time. One Earth day is 24 hours long! Earth orbits the sun in 365 days! This makes one Earth year 365 days long!
Earth is the only planet in our solar system where humans, other animals, and plants can live. There is plenty of water to drink or to live in. Water is present on Earth in its big oceans and in the air! Clouds are made of water vapor. The atmosphere has a lot of oxygen in it for animals to breathe, but the rest of our “air” is made up of water vapor, nitrogen, carbon dioxide, and other gases. The air is perfect for plants to grow. Earth temperature is not the same in all places, but the temperature is just right for plants, animals, and humans in most places on Earth.
Like the other inner planets, Earth has volcanoes. Volcanoes on Earth are different from those on other planets, because they still erupt. Scientists think that there may be active volcanoes on other planets and moons in our solar system, but they are still studying this.
Earth has one planet which we call the Moon. The surface of the Moon has many craters on it These were caused when meteorites hit it. It has many volcanoes on it which do not erupt anymore. We can see the moon at night without using a telescope. It is the closest space object to our planet ,Earth.
68.Earth is called the Water Planet,______.
A. because animals need water         B. the water makes it look blue from space
C. it has liquid water on its surface      D. Earth is the third planet from the sun
69. It takes Earth ______to orbit the sun in one year.
A.24 hours                   B.24 days                     C.365 days                   D.360 days
70. Life exists on Earth,______.
A. because the water, air, and temperature are just right
B. there is water vapor in clouds
C. Earth is the planet closest to the sun
D. earth has volcanoes
71.The craters on the moon were caused by______.
A. meteorites hitting its surface              B. active volcanoes
C. volcanoes which do not erupt anymore      D. some reasons that are not mentioned

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