Which of the following sentences correctly uses inversion in a hypothetical conditional clause?

以下哪个不是栈的应用场景？

在Java程序中，若要将程序内部产生的数据写入到硬盘上的文本文件中，应该使用以下哪种类型的流？

A legal document states: 'The defendant's testimony, though seemingly consistent with the prior statements, upon closer examination revealed inconsistencies regarding the timeline of events.' What does this statement imply about the defendant's testimony?

在TCP连接的四次挥手中，最后一个ACK包的作用是什么？