现在完成时态
⑴由have/ has ＋ 过去分词
⑵表示过去发生或已经完成的某一动作对现在造成的影响或结果
常与already, just , yet , ever, never 连用
Have you finished your work yet？你完成了你的工作了吗？
Yes, I have. I have just finished it. 是的。我刚刚完成了。
I have already finished it . 我已经完成了。
Have you ever been to China? 你曾经去过中国吗？
No, I have never been there. 没有，我从来也没有去过。
⑶①表示过去已经开始，持续到现在的动作 或状态和表示过去某一时刻延续到现在（包括现在在内）的一段时间的状态连用如：（for + 时间段，since + 时间点，或过去某一动作， 以及how long ）
②注： 非延续性动词在现在完成 时态中不能和for, since 引导的表示一段时间的状语的肯定句连用。
应转为相应的延续性动词 如：
buy---- have die---- be dead join ---- be in
borrow----- keep leave---- be away
I have bought a pen.------ I have had a pen for 2 weeks.
The dog has died.------- The dog has been dead since last week.
⑷①have (has) been to + 地点 去过某地 已经回来
②have (has) gone to + 地点 去了某地 没有回来
③have been in + 地点 一直呆在某地 没有离开过 如：
She has been to Shanghai. 她去过上海。(已经回来)
She has gone to Shanghai. 她去了上海。(没有回来)
She has been in Shanghai for 2 days.她呆上海两天了。(没有离开过上海)
1.情态动词must, may , might, could, may , can't表示推测含义与用法后面都接动词原形，都可以表示对现在情况的揣测和推断但他们
含义有所不同
must 一定 肯定 (100%的可能性)
may, might, could有可能，也许 (20%－80%的可能性)
can't 不可能，不会 (可能性几乎为零)
The dictionary must be mine. It has my name on it.
The CD might/could/may belong to Tony because he likes listening to pop music.
The hair band can't be Bob's. After all, he is boy!
2. whose 谁的 疑问词 作定语 后面接名词
如：Whose book is this? This is Lily's.
3. belong to 属于 如：
That English book belongs to me.
4. 当play 指弹奏乐器时，常在乐器前用定冠词 如：
play the guitar play the piano play the violin
当play 指进行球类运动时，则不用定冠词 如：
play football play basketball play baseball
5. if引导的条件状语从句，主句用一般将来时，从句用一般现在时代替将来时 如：
If you don't hurry up, you'll be late.如果你不快点，你将会迟到
6. if you have any idea== if you know 如果你知道
7. on 关于（学术，科目）
8. try to do sth. 尝试做某事 如：I try to climb the tree. 我尝试爬树。
9. because of , because
because of + 名词/代词/名词性短语