完成式的

Do not use the present perfect if the situation now is different.

不使用现在完成式当现在的情况是不一样时。

We use the present perfect of to be to say that someone has visited a place and come back.

记住当我们谈论过去的经历时。我们通常使用现在完成式。

First of all, the tense of both verbs is in the

首先，这里所用的动词时态是未完成式。

Despite wearing a wetsuit, neoprene cap, and regular swim cap, I was hypothermic when I finished the swim.

尽管穿了湿式保暖衣，氯丁橡胶帽和泳帽，我还是在完成比赛的时候体温很低。

Ex : j Until now, I have not seen any audience.k Up to now, I have not been able to forget how nervous I wasat that time.

until now / up to now是表示从过去到现在的一段时间，因此要用「现在完成式」来表达。

Or Microsoft conundrums where 'the progress bar may appear to indicate that loading of the document has finished when it is still in progress.

或者出现微软式的谜语进度条可能显示文件下载已经完成，事实上下载仍在进行中。

Advantages of the portable sand-dust separation device are: structure is simple, operation is convenient, sediment of sand and removal of dust can be completed during sand absorption works, work efficiency and effect for the gas absorption type boring tree planter can be increased.

本便携式沙尘分离装置结构简单、合理，操作方便，可在吸沙作业中完成沙子的沉降和除尘，提高气吸式成孔植树机作业效率和作业效果。

To say what you wish about the past , you use the past perfect

要表达对过去的希望，用过去完成式

That are far from past perfect.

不太完美的过去完成式

S+ Ved ... after S had p.p.

过去完成式是用在两个过去发生的动作有先后顺序时

This one mode pays close attention to network credence foundation of the businessman very much.

这一模式非常关注商人的网络信用基础。

Cell morphology of bacterial ghost of Pasteurella multocida was observed by scanning electron microscopy and inactivation ratio was estimated by CFU analysi.

扫描电镜观察多杀性巴氏杆菌细菌幽灵和菌落形成单位评价遗传灭活率。