Laughing is good for us. 【小题1】

Laughing involves taking quick deep breaths and then exhalations at intervals, which stimulates blood flow. A study shows that blood pressure that increases and then decreases becomes lower than it is before the laugh.

If you are feeling aching, turn on your favorite comedy. A good laugh from the heart offers relief to those who suffer from pain. With humor therapy, laughter yoga, plus your own favorite comedy to watch, laughing may be the most fun form of medicine!

When you laugh, especially from the belly (腹部), you are using many muscles. Along with laughter comes increased breathing which, in turn, sends blood that has been enriched with oxygen to the brain and throughout the body. This natural form of exercise even burns calories. 【小题3】 You could burn 10 to 40 calories after 10 to 15 minutes of laughing!

The act of laughing is something to increase those feel-good hormones called endorphins. These endorphins make people feel uplifted. 【小题4】 Besides, you will enjoy increased brain activity plus cognitive functioning.

Aside from eating a healthy diet and taking vitamins, a good dose of laughter is important. 【小题5】 A regular dose of laughter therapy can help improve the immune system and contribute to overall well-being.

Living in the wild can be hard．Finding food and staying safe aren't easy．Each day, animals try to survive in their habitats．Not all animals get by on their own. Some animals form a close partnership with other kinds of animals．These pairings are called symbiotic(共生的)relationships．

In a symbiotic relationship, the animals depend on each other．One animal helps the other meet its needs．Sounds good, right? Not always．Some animals are not very kind to their partners．In some cases, one animal meets its needs but hurts its partner．Take ticks(扁虱), for example．These insects suck blood to live．To get blood, they attach themselves to other kinds of animals．Ticks can pass germs（细菌）that cause disease instead of helping their hosts．

In other relationships, animals don't treat their partners so poorly．Both animals benefit from living with the other animal．

Small animals called cleaner shrimps(清洁虾）have found a way of helping fish．As their name suggests, the shrimps clean the fish．They hang out at what scientists call a cleaning station．A fish stops by．Then a shrimp climbs onto the fish and even steps into the fish's mouth．The shrimp uses its tiny claws to pick stuff off the fish's body．That can include dead skin and tiny pieces of food that can hurt the fish．The fish gets a nice cleaning．The shrimp enjoys a tasty meal of fish trash．

Small birds called plovers（灰斑）are also in the cleaning business．They have big customers-crocodiles.Crocodiles have long noses filled with sharp teeth. Cleaning them is funny. When a crocodile opens its mouth, the plover hops right in．It lets the plover eat small, harmful animals attached to the crocodile's teeth．The plover gets an easy meal while the crocodile gets clean teeth．

A terrifying example of the sea’s power saw about 200,000 people die in 12 different countries last week. The devastation was caused when a massive earthquake sent tsunamis smashing into Indian Ocean coastlines.

Communities in Sri Lanka, Indonesia, Thailand, India, Malaysia and East Africa have been destroyed by the monster waves. Whole towns were simply swept aside by the power of the water. Cars, trains and buildings could not survive, let alone the people who stood in the way.

The earthquake measured 9.0 on the Richter scale and occurred off the coast of Indonesia. It was recorded as the fifth strongest since 1900. Scientists said the quake was as powerful as a million of the atomic bombs that were dropped on Japan during World War II. “This may be the worst natural disaster in recent history because it is affecting so many heavily populated coastal areas,” said Jan Egeland, a UN official.

Because such waves rarely happen in the Indian Ocean, there is no system in place to warn coastal communities they are about to be hit.

Tsunami is Japanese for “harbour wave”. They are usually caused by a sudden rise or fall of part of the Earth’s crust (地壳) under the ocean. Tsunamis often happen in oceans and they are most common in the Pacific. Normally a tsunami includes a series of waves, which can be very long——as much as 100 kilometres——and be as far as one hour apart. They are able to cross entire oceans without losing much energy. One of the most striking facts about tsunamis is that an earthquake on one side of the Pacific Ocean can cause giant wave, and destruction on the other side.

When the ocean is deep, tsunamis can travel unnoticed at speeds of up to 800 kilometres per hour. They can cross the entire ocean in a day or less. The wave may only be a few metres, high in the ocean but when it is near the shore and reaches shallow water, the wave builds up very quickly in height. Witnesses in some areas of Indonesia reported seeing up to 10-metre high waves crash into the shore.