The simple subject is the main word or words in the complete subject of a sentence.
The complete subject includes all the words that tell whom or what the sentence is about.
![group image](https://smrt.sfo2.cdn.digitaloceanspaces.com/core/LMLA/KIDS/ENGL125Kids/unit05/Grammar%205-4/5-4g1.jpg)
The hardest problem was separating water and oil.
![group image](https://smrt.sfo2.cdn.digitaloceanspaces.com/core/LMLA/KIDS/ENGL125Kids/unit05/Grammar%205-4/5-4g2.jpg)
Many farm children raise pigs for fun.
![group image](https://smrt.sfo2.cdn.digitaloceanspaces.com/core/LMLA/KIDS/ENGL125Kids/unit05/Grammar%205-4/5-4g3.jpg)
The finest cake won the baking contest.