點用Present Perfect?

在英文中，動詞是有不同模式去表達時態。主要分為
- present tense
- present participle （用在進行式或延續式中）
- past tense
- past participle （用在 分詞和被動形態）
Be 這個字是屬於 irregular verb 。
Be 也是這個動詞的 original form。這個動詞的變化如下：
present tense present participle past tense past participle
(I) am being was been
(We/You/They) are being were been
(He/She/It) is being was been
Present Perfect tense
若是 positive 句子：
主詞 (subject) + has / have + past participle
若是 negative 句子：
主詞 (Subject) + has / have + not + past participle.
若是問題，要將 has / have 掉在主詞前面：
Has / Have + subject + past participle
因為 BE 的 past participle 是 been, 所以在 Present perfect tense 就要用 been.
如果仍有疑問，可以到我的信箱留言。


2009-01-29 18:13:14 補充：
BE 這個字用在 present tense 時，是要按 主詞變更的。例如：

I am a girl.
We are friends.
You are a boy.
He is a boy.
She is a girl.
It is a dog.
They are happy.

但在 aux words 和 to 的後面要用動詞的 original form. 不用 is/am/are/was/were, 而要用 be。例：
Mary will be a singer in the near future.
It might be possible.

2009-01-30 14:37:18 補充：
例子：

Present tense: Tom is singer.
Past tense: Tom was a singer but his profession was changed.

2009-01-30 14:38:40 補充：
Present perfect tense:
Positive: Tom has been a singer.
Negative: Tom has not been a singer.
Question: Has Tom been a singer?

2009-01-30 14:41:17 補充：
在 Present Perfect Continuous tense, 主要的動詞並不是 "BE" 。
Be 放在 have / has 後面要用 "been" 而作用就如 Present tense 的 "is/am/are" 或 past tense 的 "was/were".

例子：
Tom has been living in this house since 2005.

"be" is mainly used in " present tense" or " future tense".
I want to be a singer. <------( present) to be
Be happy <-------------- be + adjective
I will be okay. <------------- be + okay ( adjective) future tense(will)
I will be having dinner with my family at 8 this evening. ( future continuous tense)
It seems to be working. present to +be+ verb+ing
____________________________________
" been" appears in present perfect tense
1) I have been to Japan ten times. <-----------( to talk about your past experiences)
It means UP TO NOW you have been to Japan ten times.
已經or 曾經 = have
been = past participle (be的過去分詞)
to = preposition
The sentence structure goes like
he/she/it/ + has + been + to + ( place)
They/we/you/I + have + been+ to+ ( place)
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Passive voice被動式 in present perfect tense
been:
I have been punished ( past participle) passive voice被動式
been punished <----= 被,處罰
he/she/it + has + been + past participle = passive voice
they/we/you/I + have + been + past participle = passive voice
--------------------------------------------------------------------------
Present perfect continuous tense
We use" been" too.
1) I have been singing since this morning.
I started singing this morning and UP TO NOw I am still singing.
( This action has been going on NON-stop UP to this moment.)
One more example for you

2) My sister is really talkative.
She has been talking on the phone since 9 am.
( If it is 3 pm in the afternoon, she has been talking on the phone
for 6 hours.)

he/she/it + has + been + verb+ing + ( since, for, etc)
they/we/I/you + have + been + verb+ing ( since, for,etc)

Your sentences will be clearer with " since or for".
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Here is a table of irregular verbs for you
http://en.wiktionary.org/wiki/Appendix:Irregular_verbs:English
That's it.
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