there has been a big increase in prices.

问题描述:

there has been a big increase in prices.
请问词句怎么是什么句型?
另外,an increase in是固定结构嘛?
希望有例句,

这是 there be 的完成时:物价涨幅很大.
an increase in sth 在...有增长,例如:
There has been a big increase in the population.人口增长幅度很大.