For example, present becomes past, and past becomes past perfect.

比如，现在变成过去，过去变成过去成。

With this grammar, you're going to use the past perfect.

有了这个语法，你就会使用过去成。

They're not expecting you to use all past perfect because that just wouldn't make sense and it wouldn't make for a readable essay.

他们没有期待你都用过去成，因为这样说不通，且无法一篇可读的论文。

I had never been to, okay, past perfect.

I had never been to，过去成。

And instead of using past perfect forms he uses past simple forms.

这里，他没有用过去成用了一般过去。

That's an example of the past perfect.

" had departed" 就过去成。

This is the present perfect continuous, the past perfect uses had.

这现在成进行，过去成使用的 had。

But the last questions can be conditionals present or past perfect.

但最后一个问题可以条件句现在成或过去成。

And finally, the conditional perfect continuous; I would have been eating chocolate.

最后成进行条件句（过去将来成进行）；我会一直吃巧克力。

Mistake number five, past simple or present perfect.

第五类错误，一般过去还现在成。

In this sentence, had forgotten is the past perfect tense.

在这个句子中，had forgotten 过去成。

It was past perfect and the verb was " had studied."

它过去成，动词 had studied。

However, in spoken English, Americans sometimes use the simple past instead, like this: " I wish I studied harder for the entrance exam" .

但，在英语口语中，美国人有会用一般过去不过去成，例如：" 我当初要努力准备入学考试就好了。"

You can also use if only plus the past perfect, like this: If only I'd kept my Spanish going.

你也可以用 if only 加上过去成，像这样：要我能继续学西班牙语就好了。

But while we wait for Pete, let's talk about a new verb tense: Past Perfect.

但在我们等皮特的候，我们来谈谈一个新的态：过去成。

The perfect tenses by which I mean the present perfect and the past perfect tenses are quite challenging.

我指的现在成和过去成的成态相当具有挑战性的。

And past perfect, I was able to add it in.

然后过去成，我能够加入它。

Again, specific details: past simple or past continuous; general experiences until now: present perfect.

再次强调，具体细节：一般过去或过去成；直到现在的一般经历：现在成。

When you are talking about regrets about the past, you can use WISH with the past perfect.

当你谈论对过去的遗憾，可以用 WISH+过去成。

If something didn't happen and you want to be specific, use the past perfect form of 'hope'.

如果某事没有发生，你又想说得具体些，可以用 hope 的过去成。