真係好急.聽日要.之前問錯左...英文句子錯處.20分

(1) {A.By the end of this year, we shall graduate from school.
{B.By the end of this year, we shall have graduated from school.
(2)[A.The pianist performed in one thousand shows by 2nd April this year.
[ B.The pianist had performed in one thousand shows by 2nd April this year.
上面兩組句子，每一句的關鍵字是前置詞(preposition) by。By一個時日，意思是那個時間之前，就已經發生某一件事，用的是完成式(perfect tense)
所以1B.By the end of this, we shall have graduated(future perfect tense) from school.
和2B.The pianist had performed(past perfect tense) in one thousand shows by 2nd April this year. 是對的。而 1A和2A不對。

前置詞(prespostion) at和on 則不同。At/On一個時/日，意思是在那一個時/日，某一件事發生，用的是普通simple tense。
1A 和 2A句子，用at 代替by之後，也是正確的句子，但意思和 1B, 2B 句子不同。:
1A.At the end of this year, we shall graduate(simple future tense) from school.
2A.The pianist performed(simple past tense) in one thousand shows on 2nd April this year.




2009-01-06 08:31:25 補充：
1A 和 2A句子，用at 代替by之後..，應是...用at/on 代替...

2009-01-06 08:37:12 補充：
For oral.

'By' in front of a date/time means that something has already happened before that time, so 'by' is the correct preposition to used only in the "B "sentences which are in perfect tense.

2009-01-06 08:37:49 補充：
"A" sentenses are in simple tense, so 'at/on' should be used in place of 'by' to make them correct.

In both sentences, you're talking about something that would have happened at the specified time (ie. 已經發生)

For example,

1) "by the end of this year" we 已經 graduated from school.
2) "by 2nd April this year" the pianist 已經 performed 1000 shows.

Because of this, you would use "have graduated" and "had performed".