[Q]: - Solution caves are formed in limestone and similar rocks by the action of water - After a rain, water seeps into cracks and pores of soil and rock - The water percolates beneath the land surface - Some of the water reaches a zone where all the cracks and pores in the rock are already filled with water - Rainwater absorbs some carbon dioxide as it passes through the atmosphere and even more as it drains through soil and decaying vegetation - The water combines chemically with the carbon dioxide - A weak carbonic acid solution is formed What might be the last step of the process?
****
[A]: This acid slowly dissolves calcite, forms solution cavities, and excavates passageways

[Q]: - Acid rain is produced by chemicals that reach into the atmosphere - Falls onto the ground - The acid rain starts scouring rocks - Destroys vegetation What might be the last step of the process?
****
[A]: The lack of vegetation alters the surrounding environment.

[Q]: - Pollution enters natural water sources such as rivers and lakes - The pollution negatively affects the water quality - The pollution negatively affects the health of plants and animals - The plants and animals have shorter, less healthy lives - The plants and animals do not reproduce very well - The number of plants and animals decreases over time - The quality of water gets worse and worse as there are no plants or animals to clean it What might be the last step of the process?
****
[A]: Eventually there is nothing living in the water and it is unusable

[Q]: - The blood sugar drops in a body - Cells in the pancrease release glucagon - The liver in response turns the glucagon into glucose - And releases it into the blood What might be the last step of the process?
****
[A]:
The blood sugar levels are restored.