【问】 I am not sure but that spring has arrived.请问句中的but that是什么词，具有什么含义?

【答】 but that用在to know，to be sure，to believe，to think，to say，to imagine等动词之后，其含义是：that... not。所以现在有一种倾向用that...not来代替but that。例如：

1.I don't know but that he may come here tomorrow.

我不知道他明天可能不到这里来。

2. Who knows but that we may make friends with these foreigners?

谁知道我们不会同这些外国人交朋友呢? (我们也许会同这些外国人交上朋友的。)

3. Who knows but that we may make a forture? (MD)

谁知道我们不会发财呢?

4. I could hardly believe but that it was all real.

我很难相信这不是真的。