What is the missing first step of the following process: - 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 - This acid slowly dissolves calcite, forms solution cavities, and excavates passageways -
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Answer: Solution caves are formed in limestone and similar rocks by the action of water

Q: What is the missing first step of the following process: - Over time, more sediment piles on top - The resulting heat and pressure transforms the organic layer into a dark and waxy substance known as kerogen - Left alone, the kerogen molecules eventually crack - The molecules break up into shorter and lighter molecules composed almost solely of carbon and hydrogen atoms - It will turn into either petroleum or natural gas -
A: Dead organic material accumulates on the bottom of oceans, riverbeds or swamps, mixing with mud and sand

Question: What is the missing first step of the following process: - The sediment rolls down hill towards a river - The heavy items sink to the bottom - The lighter items float on the top and in convection cycles - As the river flows the sediment is moved - The sediment gets dumped through tributaries into lakes and the ocean - The sediment keeps moving around the world in convection currents.
Answer: Sediment becomes loose from the rest of the soil

[Q]: What is the missing first step of the following process: - Nephrons in the kidney filter the blood - The waste that is filtered out mixes with water - Become urine - Ureters carry urine out of the kidneys.
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[A]: Blood carried into kidney by the renal artery

input: Please answer the following: What is the missing first step of the following process: - The spore lands on a piece of bread - The spore grows hyphae into the bread - The mold forms a colony - Sporangiophores grow upward - The mold sends out spores.
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output: A mold spore floats through the air

What is the missing first step of the following process: - The spores fall to the ground - The spores germinate - The spores begin to grow mycelium - The mycelium begin to sprout a bud - A new mushroom is formed.
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Answer:
Spores are dispersed into the air by a mature mushroom