Question

一个很难的英语句子的结构分析

Then gradually between about AD 800 and 1150, English became less like German because those who ruled England spoken first Danish and later French.

1、分析前半句“Then gradually between about AD 800 and 1150, ”的结构
2、说明because在句中是连词还是介词。说明理由。谢谢
句子的出处，给出：
So why has English changed over time? Actually all languages change and develop when cultures meet and communicate with each other. At first the English spoken in England between about AD 450 and 1150 was very different from the English spoken today. It was based more on German than the English we speak at present. Then gradually between about AD 800 and 1150, English became less like German because those who ruled England spoken first Danish and later French. These new settlers enriched the English language and especially its vocabulary. So by the 1600’s Shakespeare was able to make use of a wider vocabulary than ever before. In 1620 some British settlers moved to America. Later in the 18th century some British people were taken to Australia too. English began to be spoken in both countries.

Answer 1

前半句：前半句是表示时间的状语，其中then 和gradually都是副词，他们作为副词的位置是比较自由的，其中then表示“那时”多英语句首或者句尾，本句中句首比较合适，因为主句比较长；而gradually也可以放在主句中become前面。主要部分是between。。。1150。
because是并且只是一个连词。 because不能作为介词。连词引导句子，介词后跟名词或者动名词等成分，两者是不同的。另外，比如说because of是一个介词短语，可以说because of the rain,但是如果用because的话就必须这样说because it rains。
希望能帮到你。

Answer 2

“Then gradually between about AD 800 and 1150, ”的结构
gradually ，副词，逐渐地，可以单独放句首，这里的gradually 修饰between about AD 800 and 1150，表示“慢慢地，在公元800年到1150年间”的意思
because在句中是连词，连接两个句子，because 后面的句子省略了谓语动词，这可能是他们的写作习惯吧