Dogs have a different way of seeing the world compared to human beings. As a result of this they heavily rely on their body language to pass their different messages across to people. 【小题1】

Dogs bark for different reasons. If you notice them barking very often and loudly, they bark for an urgent reason probably. 【小题2】 It could also be a sign that they are in some kind of pain. When the barks are shorter and also softer, they probably just want to play around. Pay attention to the barks closely so that you understand exactly what is going on.

【小题3】 When you see your dog making sad faces while you are leaving, it might feel sad. Don’t worry too much because your little pet knows very well that you will definitely be back.

Dogs like to lay on people’s feet during dinner time or when people are watching TV. 【小题4】 However, it’s just their way of showing you some loyalty (忠诚) and how close they want to get to you. This is a behavior that they obtained from their ancestors long ago.

You should feel honoured when a dog rests against you for support while it’s hanging around the place. 【小题5】 Don’t take it as being lazy. The next time your dog does this, just allow them to show their love in this way.

Unsolved Mysteries About the Planet Earth

◆Mystery 1: Where did all the water come from?

Water covers 70 percent of Earth’s surface and earns it the nickname “the blue planet”. And where did it come from? The most popular scientific theory states that the water came from several violent asteroids (小行星) filled with ice. Another suggests that the water actually has been around since Earth’s formation. However it happened, though, it’s certainly worked out well for Earth’s life forms.

◆Mystery 2 :What about all the oxygen?

Another thing is the planet’s oxygen. Tiny creatures released oxygen as a waste product, filling the atmosphere with it. After that, the level of oxygen in Earth’s atmosphere went wildly up and down until it finally calmed down around 540 million years ago. Since then, it’s remained at about the breathable level we experience today. But what caused it to be suddenly steady?

◆Mystery 3: What caused the Cambrian (寒武纪) Explosion?

The Cambrian Explosion refers to the explosion of complex life forms that occurred on Earth about 540 million years ago. Before then, life had consisted mostly of bacteria. But at the beginning of the Cambrian period, complex creatures began developing at a rate never seen before. Suddenly, life forms had brains, eyes, and bones. Most living creatures today can trace their blood back to the Cambrian period.

◆Mystery 4: Will we ever be able to predict earthquakes?

We still haven’t been able to come up with a way to accurately predict earthquakes. We can certainly try, but our current technology cannot predict them exactly. We know that earthquakes start when rocks crack underground and send earthquake waves toward the surface, but we haven’t figured out why that happens, or how to predict it.

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