A. enough B. serious C. resource D. centuries E. precious |
From deserts to beaches to playgrounds，sand is found almost everywhere.It is a common sight.But you might not know that it is very.
Sand is widely used in glass-making and road-building.It is the second most-used after water in the world，the BBC reported.However，the UN said that sand is not limitless and that we might be running out of it.
Sand is made up of very small pieces of rock，soil and minerals.It can take thousands of to form，but now we are using sand too quickly.According to the BBC，we use about fifteen billion tons of sand every year to build houses，roads，etc.That is to build a 20-meter-high by 20-meter-wide wall around the equator （赤道） every year.Can you believe it？
