【观察】观察下列几组句子中虚拟语气的用法，然后加以总结。
1. a. If I were you, I would apply for the job.
b. I would walk to work if I lived near my office.
2. a. You could have passed the exam if you had been more careful.
b. If you had turned off the gas, the house wouldn’t have caught fire.
3. a. If I were to do the job, I would do it in a different way.
b. The game would have to be called off if it should rain this weekend.
c. If the teacher asked me to solve the problem next time, I could try my best.
