Two good friends, Sam and Jason, met with a car accident on their way home one night. The next morning, Sam woke up blind. His legs were broken. The doctor, Mr Lee was standing by his bed, looking at him with a thoughtful expression. When he saw Sam awake, he asked, "How are you feeling, Sam?" Sam smiled and said, "Not bad, Doctor. Thank you for doing the operation  ." Mr Lee was moved by Sam. When he was leaving, Sam said, "Please don't tell Jason about it." "...  OK." Mr Lee replied. Months later when Jason's wounds   _ , Sam was still very sick. Neither could he see or walk. What he could do was just stay in his wheelchair all day long. At first, Jason stayed with him for a few days. But days later, Jason felt very discouraged and embarrassed to spend time staying with a disabled man like Sam. So he went to see Sam less and less. He made new friends. From then on, he didn't go to visit Sam any more. Sam didn't have any family or friends other than Jason. He felt very sad. Things went from bad to worse. Sam died a year later. When Jason came, Mr Lee gave a letter to him. It was from Sam. In the letter Sam said, "Dear Jason, I am disabled. But I want you to be a healthy man. So I gave my eyes to you so that you can enjoy life as a healthy man. Now you have new friends. I'm glad to see that you are as healthy and happy as usual. I'm glad you live a happy life. You are always my best friend ... ... Sam". When he finished reading the letter Mr Lee said, "I have promised that I will keep this a secret until Sam is gone. Now you know it." Jason stood there. Tears ran down his face. We can infer from the passage that   _  .
Sam drove too badly and caused the car accident the unsuccessful operation led to Sam's blindness Jason knew how Sam helped him before Sam died it was Jason that was made blind in the car accident