题目

People use money to buy food, books and hundreds of other things they need．When they work, they usually get paid in money． Most of the money used today is made of metal or paper．But in the time long ago, people used to use all kinds of things as money．One of the first kinds of money was shells． In China, cloth and knives were used as money．Elephant tusks（牙）, monkey tail and salt were used in some parts of the world．Rice was also a kind of money used by the people in some islands． The first copper coins were made in China．They were round and had a square hole in the cent下列关于常见自然现象的说法中正确的是： [     ]A．夏天揭开冰棒包装后会看到冰棒冒“白汽”，这是凝华现象 B．初冬的早晨地面上会出现白色的霜，这是凝固现象C．冬天说话时，看到 “白气” ，是口中喷出的水蒸气D．秋天的早晨花草上出现小的露珠，这是液化现象