Problem: Given the question: What is the missing first step of the following process:  -  As water expands it puts great pressure on the walls of anything containing it, including any rocks which happen to be surrounding it - The force of the pressure exerted on the rock surrounding it is enough to wedge the walls of the crack farther apart, thus expanding and deepening the crack - Clay expends when wet like ice does - This causes rock to break apart - Some plants like mosses and lichens are capable of growing without soil on bare rock - When they do this their roots penetrate pores and crevices and cause rocks to split apart as the roots force their way down through the rocks -
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The answer is:
When water freezes it becomes 10% bigger, or takes up 10% more space


Problem: Given the question: What is the missing first step of the following process:  -  Causes them to absorb aluminum from soil - The water runs off from the soil into lakes, streams, etc - Fish and their eggs die - Frogs and plants die - Insects and other wildlife die - The ecosystem is out of balance, causing further problems -
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The answer is:
Acid rain makes waters acidic


Problem: Given the question: What is the missing first step of the following process:  -  Enters the lungs - The oxygen fills the sacs in your lungs - Carbon dioxide is removed from the lungs and exhaled - The oxygen is pass throughout your body.
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The answer is:
