Question

Ms Shen gave us instructions and then we worked by ourselves then在后一句的句首怎么不倒装

Ms Shen gave us instructions and then we worked by ourselves then在后一句的句首怎么不倒装

Answer 1

1 then在句首时，不是每个句子都有倒装。下面含有then的句子可以倒装：
The man came then whom she had been waiting for for years to marry her.
-----Then came the man she had been waiting for for years to marry her.
还有，你的原句没有倒装，是因为then的后面是人称代词we做主语,没有必要倒装。如果用（比如说）名词做主语，就可以倒装了:
Then the girls worked by themselves
------- Then worked the girls by themselves (这种倒装叫方位词倒装 、 全倒装)

2 你的句子也可以倒装，但by ourselves要提前：
--------- Ms Shen gave us instructions and by ourselves did we work then.（半倒装）

Answer 2

Ms Shen gave us instructions and then we worked by ourselves then沈老师给我们说明后,然后我们自己（开始）工作。倒装句是只有，当需要强调这个句子时才采用倒装句。

Answer 3

then表示【然后】无需倒装。