阅读下面短文，在空格处填入一个适当的词或者使用括号中词语的正确形式填空。
Counting before numbers
Before the invention of written numbers,
people used many different ways {#blank#}1{#/blank#} count things.
At first, people used {#blank#}2{#/blank#} (they)
fingers, and even their toes. {#blank#}3{#/blank#}, they could only count small numbers in
this way.
After that, they began to make small {#blank#}4{#/blank#}
(mark) on sticks and bones. This helped them count {#blank#}5{#/blank#} (big) numbers. They
used them to count things {#blank#}6{#/blank#} the days of month, the amount of food and
the number of animals they had.
Then people began to use tokens made from
clay {#blank#}7{#/blank#} small stones. This helped them count even bigger numbers. They
often put the tokens on pieces of string so that they could carry them around {#blank#}8{#/blank#}
(easy). This developed into tools like the abacus.
Finally, people began to develop systems of
{#blank#}9{#/blank#} (write) marks to show different numbers, and this {#blank#}10{#/blank#} (lead) to
the Hindu-Arabic system (0-9). We are still using this system today.
