【文章內(nèi)容簡(jiǎn)介】 faster in a different direction. “It39。s like when you39。re in a bus and it makes a sudden stop， ”says Crutchfield， an expert at a sports concussion center in Baltimore， Maryland.“You hit the inside of the bus.” This hit damages the brain. It affects the way the brain functions（運(yùn)轉(zhuǎn)） . So some sports require athletes to wear help reduce the force of a hard outer shell spreads the force over a larger area. Inside a helmet，a plastic or airfilled lining also helps soften the blow. Steve Rowson is an engineer at Virginia Tech. In his lab， he tests how helmets hold up against different types of hits. No helmet can prevent concussions pletely， says Rowson. But he39。s found that when wearing a newer football helmet，the player39。s head doesn39。t gain speed as much after a lowers the risk of concussions. Many youth sports teams have set limits on physical contact to reduce the risk of concussions. In soccer， most concussions happen as a result of headers— shots or passes made with the 39。s why many people think kids shouldn39。t head the ball until high school. These efforts should help， says Crutchfield. But the best way to prevent longterm brain injuries， he says， is to stop playing immediately if you suffer concussion. “Protect yourself today so you can play again tomorrow.” 28． Concussions among young players . A． are rare before 2020 B． are mostly caused by wearing no helmets C． cause kids to lose interest in sports D． seem extremely worrying 29． The author mentions the sudden stop of the bus to . A． give a better explanation of concussions B． show human brains are easily damaged C． stress it39。s dangerous to ride buses. D． remind people to wear helmets while playing sports 30． What does Steve Rowson think of the newer football helmets? A． They vary a lot in size B． They allow the players to move their heads more freely. C． They slow down the players39。 running speed. D． They work better than the old ones. 31． suggests that after receiving a concussion， young players should . A． never head the ball B． stop playing the sport for a while C． paly other kinds of sports D． avoid dangerous sports D According to Mars Inc. and Barry Callebaut， two of the world39。s biggest chocolate makers， people are eating more cocoa than farmers can grow. That means the world is in the middle of a chocolate shortage— and it could get worse. Last year， people across the world ate 70,000 metric tons more cocoa than was produced. Chocolate makers say that shortage could reach 1 million metric tons by 2020， and 2 million metric tons by 2030. Experts say that there are several reasons for this. Higher temperatures and dry weather in West Africa， where about 70 percent of the world39。s cocoa beans are grown， have greatly hurt production there. Plant diseases have also destroyed International Cocoa Organization （ ICCO） estimates（估計(jì)） that the disease has reduced the world39。s cocoa production by 30 to 40 percent. As the shortage continues， experts say chocolate bars will get smaller and less tasty. Farmers have been producing a new strain（品種） of cacao， the seed from which cocoa is made， called CCN51. This strain is resistant（抗 ?? 的） to the plant disease and produces about seven times more cocoa beans than typical cocoa strains， but it39。s less tasty. Producers will also add ingredients such as vanilla and vegetable fat to chocolate so that they can use less cocoa， and chocolate bars will contain more fillers like nuts and raisins. At the same time， the price of chocolate has been increasing. Cocoa prices have risen by more than 60 percent since 2020. But it39。s not all doom and gloom for Central American research anization has developed more new strains of cacao that are diseaesresistant but still taste good. And some experts say the shortage has been exaggerated（夸大） .“While our estimates show that supply shortages are likely to occur during the next several years， ”the ICCO said in a statement ， “supplies of cocoa beans should last until production growth increases.” In other words， the world39。s chocolate lovers may not need to panic just yet. 32． The main reasons for the cocoa shortage are . A． hot and dry climate and plant diseases B． high temperatures and loss of land C． cold weather and a water shortage D． environmental damage and people39。s waste 33． What do we know about C