Have you ever been in a plane? 你坐过飞机吗? The new books have not arrived yet.新书还没有到。
The Xisha lslands have always been Chinese territory.西沙群岛一直是中国的领土。 Have you heard from him yet? 你接到他的信了吗?
They have already finished their experiment.他们已经做完试验了。
Many westerners have never seen a giant panda.许多西方人从没见过大熊猫。 We have often been to the Summer Palace.我们常到颐和园去玩。
3)现在完成时可以和包括“现在”在内的时间状语连用，如now，today，this month，this year等。如：
We have planted many fruit trees this year.我们今年种了很多果树。 Have you seen Benny today? 你今天见到本尼了吗? We've had a lot of rain this summer.今年夏天雨下得很多。
但如说话人所感兴趣的只是在这段时间内发生了某一动作，而不是这一动作与现在的关系时，须用过去时态。如：
The conference opened this month.会议是本月开幕的。
Their farm set up a pumping station this year.他们农场今年新修了一个抽水站。 现在完成时可和疑问副词where，why，how连用，但通常不和疑问副词when连用 (when一般只与过去时态连用)。如：
Where have you been? 你去哪儿了?(询问经过情况。如说Where did you go?则只问地点) Why have you turned off the radio? 你干吗把收音机关了?(强调和现在的关系，意即收音机关着。如说Why did you turn off the radio?则强调关收音机这一过去的动作。)
Sometime”是个时间副词，意思是“在某时期”。这个字通常 和“日期”或“时间”连用，出现在句子后半部， 用来固定本来不肯定的时间或日期。例如： ① The accident happened sometime last month ② Let us discuss the matter sometime next week.
*“Sometimes”是个频率副词（adverb of frequency），意思和 “occasionally”，或“from time to time”甚接近，就是“有时候”或“偶尔”之意。 “Sometimes”和“sometime”不但意思不同， 所处的位置也不一样。
“Sometimes”可以在下列三处出现： ⒈句首，如：
Sometimes, I didn't feel like working. ⒉接系动词“be”之后，如：
The new manager was sometimes very hot-tempered. ⒊动词前，如：
They sometimes stayed up until 2 o'clock.
从这三个例子看，“sometime”和“sometimes”不但意思不同 ， 所处的位置也大相径庭。
就用途来说， “sometime”的用途广些。除了表示“在某时期 ”这意思之外，它也含有“任何时候”的意义，如：
* Come over and see me sometime.
这里的“sometime”，可以用“anytime”代替，即： * Come over and see me anytime.
此外，“sometime”可以当形容词用，意思是“以前的”，如： * Dr Chen, a sometime lecturer of chemistry, is now a big company director.
这里的“sometime”不妨以另外一个形容词“former”或前缀“ ex-”来取代： *Dr Chen, a former lecturer of chemistry, is now a big company director. * Dr Chen, an ex-lecturer of chemistry, is now a big company director.
**另外，“sometime”和“some time\的意思不同。“Sometime”是“在某时期”；“some time” 是“一段时间”，如：
*All of us have studied English for some time. * Betty has been grumbling for some time.
* Please give me some time to think over your proposal.
由于 sometimes, sometime和 some time 各有不同的意思，在同句里出现可以和平共处、相安无事：
* Sometimes, I spent some time reading a sometime English lecturer's novel written sometime in 1996. （有时，我花了些时间阅读前英语讲师在 1996 年某时期所撰写的一本小说）
初中现在进行时讲解练习及答案
