1. No one can solve this problem.
-> This problem............................
2. Minh last met his penpal five months ago.
->Minh hasn't.........................................
3. Jack London writes many exciting novel. He said
-> He said.....................................................
4. What a pity! I can't help you now.
-> I wish I...........................................
1. No one can solve this problem.
-> This problem can't be solved
2. Minh last met his penpal five months ago.
->Minh hasn't met his penpal for five months
3. Jack London writes many exciting novel. He said
-> He said Jack London wrote many exciting novels
4. What a pity! I can't help you now.
-> I wish I could help you now