From deserts and beaches to playgrounds, sand is everywhere. But you might not know that sand is also 【小题1】 useful resource (资源). Sand is the second most-used resource in the world after water, the BBC reported. However, the UN said that sand is limited (有限的) and that we might be using it up.

Sand is made up of very small 【小题2】 (piece) of rock, soil and minerals (矿物质). It can take tens of thousands of years to form (形成) . But now we are using sand more 【小题3】 (quick) than it is being formed. According to the BBC, we use about 15 billion tons of sand every year to build houses, roads and other things.

Also, sand 【小题4】 (put) in the sea to make new islands. For example, the Palm islands are made up of three large man-made islands in Dubai, United Arab Emirates. In 2010, they 【小题5】 (take) 94, 000, 000 m³ of sand to build. If people keep 【小题6】 (use) too much sand, it will run out in many places. For example, Vietnam may run out 【小题7】 construction (建筑) sand by 2020, Live Science noted.

【小题8】 people need so much sand, they are trying to mine (开采) more of it. But this is 【小题9】 (harm) to the environment. Mining sand may cause beaches to disappear 【小题10】 more floods to happen in places close to the sea. Also, this may affect the habitats (栖息地) of many plants and animals.

It can be hard to know what newborn babies want. They can't talk, walk o【小题1】 even point at what they're thinking about. Yet babies begin to develop language skills long before they begin speaking. And, c【小题2】 to adults, they develop these skills much more quickly. People have a hard time learning new languages as they grow older, but babies have the ability to learn any language e【小题3】.

New research strategies（策略） have helped scientists to discover that babies begin life with the ability to learn any languages. By interacting（互动） with other people and by u【小题4】their excellent listening and observational skills, they quickly learn the languages they hear most often.

Because babies can't tell scientists what they're hearing, scientists have been using a different method to c 【小题5】 if they can tell one sound from another. In some e【小题6】for example, scientists play recordings of a sound, such as "eee" over and over on one side of a baby's head. Then, they play another sound such as "aaah," to the baby's o【小题7】 side. If the baby turns to the new sound, he will see a dancing toy—a p【小题8】that encourages him to respond to such changes. If he doesn't turn, that suggests that he doesn't hear the difference b【小题9】 the sounds. The studies have shown that, by about six months of age, babies have been able to recognize all the s【小题10】that make up all the different languages in the world.