Here are some suitable words to fill the blanks:

1. **illustrates**
2. **provides**
3. **and**
4. **various**
5. **relied**
6. **reach**
7. **include**
8. **with**
9. **did**
10. **to**
11. **have**

So the completed text would read:

There is no doubt that money, in the form that we know it today, (1) **illustrates** what keeps modern economic life functioning. Yet, throughout history, money, in whatever form, has provided (2) **provides** the ability to buy (3) **and** sell goods. Thousands of years (4) **various** civilisations (5) **relied** on the barter system as a way of exchanging goods. Within this system a person had to exchange one thing for another. This meant that the two parties involved had to (6) **reach** an agreement as to what they thought their products were worth. Items such (7) **include** wheat, tobacco and livestock have all been used as money at one time or another. It was not until much later (8) **with** the idea of money in the form of metal coins. So (9) **did** the barter system come to an end? The answer is simple. Coins were much easier to handle and carry around. Since then, the use of coins has become widespread. It has made (10) **to** develop business with other countries further afield, which they (11) **have** never done business with before.

In recent years, paper money has become more common all over the world, as it is easier to use. It (12) **will** not be long, however, before plastic cards take over completely, replacing coins and paper money.