① I would have known it beforehand in your position.

= If I had been in your position, I would have known it beforehand.

② A hundred years ago not a doctor could have carried out such an operation.

③ One's memories of any period must necessarily weaken as one moves away from it. At twenty I could have written the history of my schooldays with an accuracy which would be quite impossible now.

④ I would be happy to be of any service to you.

⑤ Nobody but a complete fool would have believed such a thing.

⑥ Any girl dressed like that would be laughed at.

⑦ No other man could do the work.

⑧ Just a piece of bread and a glass of milk would satisfy me.