Question

介词放句首句子一定都全倒装吗

Answer 1

不一定.

1. 如果是“介宾 + be/不及物动词 + 主语（名词）”结构,则须倒装.

如：In the middle of the school is/lies a teaching building.

即倒装时,必须要求句子主语必须为名词（短语）,动词必须是be动词/不及物动词.

2. 如果没有上述特点,则无须倒装.

如：On the playground I found a purse.

= I found a purse on the playground.