Task: Sentence Ordering
Input (English): Solution caves are formed in limestone and similar rocks by the action of water
A weak carbonic acid solution is formed
Some of the water reaches a zone where all the cracks and pores in the rock are already filled with water
After a rain, water seeps into cracks and pores of soil and rock
The water percolates beneath the land surface
The water combines chemically with the carbon dioxide
Rainwater absorbs some carbon dioxide as it passes through the atmosphere and even more as it drains through soil and decaying vegetation
This acid slowly dissolves calcite, forms solution cavities, and excavates passageways
Output (English):   No