高一文法問題!! 這樣為什麼錯

She did not know what to do, so she began to cry.（有因果關係）
She did not know what to do, and began to cry.（只是先後關係，未強調因果）
口語常用simple sentence或compound sentence，而不用complex sentence，可以依上面之一來說。

Didn't know what to do, she began to cry.這樣是不符英語語法的。因為前一句沒有主詞，前一句和後一句沒有連接詞，結果讀者分不出那裡是焦點，也看不出因果邏輯關係。

通常寫作才會用到complex sentence或分詞構句，因為較文雅。主要子句是句子的焦點，因此用這種寫法時，條理和因果邏輯關係較分明。

Didn't know what to do, she began to cry.
可是為什麼上面那句那麼順!!!~_~

因為那句像中文。中文常常沒有主詞。"不知如何是好" - 很順。
但是英文不能這樣。

Louis + 1 ; 解釋許詳盡!

Didn'tknow what to do, she began to cry. Answer: 句子與句子要用連接詞連接 A. She didn'tknow what to do and she began to cry. = B. Becauseshe didn't know what to do, she began to cry. = C. Notknowing what to do, she began to cry. (主詞相同時可省略副詞子句的主詞和連接詞Because she，改成分詞)

2011-07-05 08:51:22 補充：
didn't know / Because she / Not knowing

句子正確此句不像口語 Because she didn’t know what to do, she began to cry.不如Not knowing what to do, she began to cry.來的好 這只是個人喜好

If I were you, I would like to rewrie it as follows:

Because she didn't know how to do it letting her began to cry.