input: Please answer the following: What is the missing first step of the following process: - The bird collects bits of sticks and grass - The sticks and grasses are placed between support branches - Leaves, mud and spider webs are added to the sticks - The mud, leaves and webs glue the sticks together - The solid nest supports the eggs -
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output: A bird picks a spot high spot, often in a tree

Please answer this: 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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Answer: Acid rain makes waters acidic

Problem: What is the missing first step of the following process: - The water combines with carbon dioxide in the air to form carbonic acid - As the acid is formed, the iron starts to dissolve - Some of the water breaks down into hydrogen and oxygen - The free oxygen and dissolved iron bond together - They form iron oxide, which is rust -

A: Water comes into contact with something made of iron

Problem: Given the question: What is the missing first step of the following process: - The matter forms on the sea floor - Layers of sediment form above the matter compressing it - After many years the matter is compressed and heated - The result is that crude oil forms.
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The answer is:
Living organisms in the sea die

input question: What is the missing first step of the following process: - Air enters bronchioles - Bronchioles have tiny air sacs called alveoli - Alveoli surrounded by small blood vessels - Oxygen absorbed by small blood vessels - Vessels deliver oxygen to every cell in the body - Blood brings carbon dioxide back to lungs - Carbon dioxide released when you exhale.???
output answer: Air enters the lungs through bronchial tubes

input question: What is the missing first step of the following process: - The sound travels in waves, as sound does - The sound "bounces" off of a nearby object - The sound wave returns to the bat - The bat hears the echoed sound - Folds in the bat's ear and adaptations in the bat's brain enable it to determine the size, shape, and position of the other object via the properties of the returned sound waves - Other animals use echolocation in generally similar ways -???
output answer:
Bats and other animals produce a high-pitched tone