Here are the correct answers based on the context provided:

1. **d. has been used** - Paper money has been used for over a thousand years.
2. **c. has** - The heat of the sun has transmitted to the earth by radiation.
3. **b. accustom** - At parties, people accustom to talk about jobs and money.
4. **a. to keep** - Are you going to keep me waiting all day?
5. **b. himself** - This model airplane is very good indeed; it is a credit to itself.
6. **b. providing** - We had difficulty providing a suitable meeting place.
7. **c. brother's** - The boy complained that someone had stolen his book and also his brother's.
8. **a. the other** - If you don’t want this pen, take the other. There are some left in the box.
9. **b. assured** - He assured the bank manager that he could repay the loan.
10. **b. tried** - You ought to have tried your best to save her, but you never tried.

Feel free to ask if you need any further assistance!