There did not use to be many cars on the road before.
Now there are..  more cars on the road than that before.
34. My brother was a professor at Ha Noi University some years ago,
My brother used.to be a professor at Ha Noi University some years ago,
35. They has built this building since 2019. (Change these sentences into the passive. )
This bulding has been built since 2019 
36..They built a hydro power station in this area last year. (Change these sentences
into the passive. )
a hydro power station was built in this area last year