用英语解释句子 The abacus is ancient invention
还要用英语解释：3.The abacus is an ancient invention.
4.The Indians invented the systen of numbers.
5.Most of my answers are accurate.
1.The invention of the zero helped people calculate more easily.对calculate more easily提问.
2.People wrote numbers in many different ways.对in many different ways提问.
3.You mustn't eat in the reading room.改为祈使句
4.people,easier,for,work,machines,it,to,make.连词成句