Choose the correct answer

Could and was/were able to (3)
0 Which is closer to the meaning of the sentence 'Years ago I could run a marathon'?
a) I ran a marathon at one particular time in the past.
b) I was once fit enough to run a very long way.
The correct answer is: b
1 Which of these sentences is correct?
I was ill, so I couldn't go to the party.
I was ill, so I wasn't able to go to the party.
a) I Only the first one.
b) I Only the second one.
c) I Both of them.
The correct answer is: 
2 Which is closer to the meaning of the sentence 'Sarah was able to leave work early yesterday'?
a) Sarah left work early yesterday.
b) Sarah had the opportunity to leave work early yesterday, but we don't know if she took it.
The correct answer is:  
GỢI Ý B3 GIẢI THÍCH GIÚP EM Ạ