【推荐1】Dolphins are not fish; they’re mammals. They are warm-blooded like man and give birth to one baby called a calf at a time. At birth a calf is about 90—130cm long and grows to about 4m. They live up to 40 years. They are highly sociable animals.

Their teeth are interlocking rows of hooks, suitable for holding slippery fish. They eat fish whole starting with head first. When they go wild they keep their mouth open and sometimes keep it nodding to express their aggression. Greater aggression is shown by violent jaw clapping. Dolphins breathe through their blowhole(呼吸孔) located at the top of their head. The dolphin’s eyes produce a special slippery secretion(分泌物) which protects the eyes from foreign objects and water friction.

Dolphins use their powerful tail to move through the water. They also use their tail while hunting. They slap their tail rapidly when they get annoyed or when they want to indicate the sign of danger to alert other dolphins.

The dolphin’s skin is completely smooth allowing the dolphin to move easily through the water, and also reduce heat loss. Their skin may bear rake marks from other dolphin’s teeth during play or mating, and can easily become badly sunburned if they strand(搁浅).

Their bodies are very streamlined so they may swim at high speed through the water, and an example of this is their ears. Dolphin’s ears are barely noticeable marked only by a small hole just behind the eyes.

While sleeping, it shuts down only half of its brain, as its breathing is under voluntary control. Dolphins take short catnaps, floating just below the surface, and then slowly rising to breathe. Often dolphins are very active during night time, for some this is their main feeding time. Dolphins are able to dive to great depths, and also leap to great heights. They may leap to avoid predators or to show how powerful they are to females at mating time.

【推荐2】Crossing your legs is an extremely common habit; most people don’t even notice that they’re doing it when they sit down. While you may find it comfortable to sit with one knee crossed over the other, it might be causing health problems that you are not aware of.

A study published in Blood Pressure Monitoring stated that sitting with your legs crossed can increase your blood pressure. The reason this happens is because the blood in your legs has to work against gravity to be pumped back to your heart, crossing one leg over the other increases resistance, making it even harder for the blood to circulate. This causes your body to increase your blood pressure to push the blood back to the heart.

Crossing your legs can also lead to neck and back pain. When you sit with your legs crossed, your hips are in a twisted position, which can cause one of your pelvic (骨盆的) bones to rotate. Since your pelvic bone supports your neck and spine, this can cause pressure on your lower and middle back and neck.

You also might notice that when you sit with your legs crossed for long periods of time, your feet and legs get tingly or have the feeling of being asleep. This is because when one leg sits on top of the other, it causes pressure on the veins (血管) and nerves in your legs and feet. It can cause numbness and/or temporary paralysis in the legs, ankles, or feet.

So next time you sit down, try to get yourself in the habit of sitting with both of your feet on the floor. Not only will it help your posture and stability, but it will also save your health in the long run.