by當"在...之前"的用法

當by解釋為在...之前時，

1. By可以放句首嗎?

"在....之前"是個副詞片語, 當然可以放在句首, 例如:
By next Wednesday all the students will have left the school.
= All the students will have left the school by next Wednesday.
在下週三以前, 所有學生們都已離開學校了.

2.By後面可以加子句嗎? 還是只能加名詞?
by+主+V... or by+名詞

介系詞By後面可以接任何名詞性質之敘述, 包含名詞子句:
例如:
By what you did for the country, you have convinced the people of your
loyalty.
以你為國家所做的事, 你已讓人民相信你的忠誠.

By what you stated to thee jury, you have proved yourself innocent.
憑你向陪審團所陳述的內容, 你已證明你的清白了.

不過, "By the fact that + S + V" 或 "By the time S + V" 等句型不算是By後面接子句, 因為這是接名詞the fact與the time, 子句是修飾名詞的.


2011-02-12 22:53:12 補充：
再舉一句:
By how you explain the issue, we can verify if you have really caught the picture.
根據你如何解釋此事, 我們可以判知你是否已真正明白了怎麼回事.

1。不可以。never think of it.

2.可以加名詞，e.g.

I will go there by 3 o'clock tomorrow.

沒有子句可以加。by+主+V... 一般情況不需要