Чем отличается could от can и couldn't от can't??? Напишите

could и couldn't используются в времени, в то время как can и can't - в настоящем

1. The jumper shrank when I had washed it.
2. Mike got really exhausted in his first marathon because he hadn't run such a long race before.
3. The light in the room showed that Mr Simpson had been waiting for me.
4. The Titanic was travelling to New York when it hit an iceberg and sank in the Atlantic.
5. The footballer was running towards the goal when he fell over.
6. George said that he hadn't decide yet which side to support.
7. I took the decision after I had spoken to him.
8. Bill had been working at the same problem for two hours when Jack phoned him and asked if he had solved it. 
9. I knew that Nick had been boarding with an American family since his arrival and he had learnt a great deal about American habits and customs. 
10. I found out why my pen friend hadn't been getting my letters. I had been sending them to the wrong address.

1) a lot of people prefer to to rent  a flat instead of buying their own.
2)tea and coffee was offered to us by the hotel, so we did not have to go down to the restaurant
3)there was no good bathroom, which was a big disadvantage. We won't stay in that hotel again.
4)all kinds of fun  in the Crimea get a lot more expensive in summer.
5)he found a job in another city and left his house for two years
6)Jane can take a holiday. She has been working day and night all these years.
7)ann is in difficult situation. She will have to borrow money to pay all her debts.
8) don't blame the student for losing the book. It has been found and returned