He didn't go to the zoo to see the feeding of birds because it was raining heavily outside.(改成简单句) He didn't go to the zoo to see the feeding of birds because of the heavy rain outside.
We all know the famous singer because she sings nicely.(改成简单句) We all know the famous singer because of her nice songs.
Lots of people know about the film because of many advertisements.(改为复合句) Lots of people know about the film because it has many advertisements.