我是不是挑了个不恰当的时间跟你谈话？
Have I picked a bad time to talk to you?
通常情况下，我是不会看到这封信的。
Normally, the letter would not have come to my notice.
我是外国人这事实对我十分不利。
The fact that I was a foreigner was a big disadvantage.
我是爱莫能助啊。
It is not within my power to help you.
我是老主顾，他们都认识我。
They know me ─ I'm a regular customer.
他谈话中使用的行话对我是一团迷雾。
The jargon in his talk was opaque to me.