Which group of sentences best uses a variety of sentence patterns to convey meaning and the relationship between ideas?

The cat curled itself into a ball. It purred. Its human scratched its chin.


The cat curled itself into a ball. Its human scratched its chin. When it felt the scratching, it began to purr.


The cat curled itself into a ball. It began to purr when its human scratched its chin.


The cat curled itself up, so it was a ball. Its human scratched its ears, so it purred.