Problem: Given the question: What is the missing first step of the following process: - Rain falls - Water is in the area of high elevation - The water creates a stream - The stream moves towards lower elevation - The stream continues along the same path for a long time - The soil and rocks erode where the stream touches them - The stream moves deeper into the soil - The stream is smaller than the eroded area.
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The answer is:
An area is at a higher elevation than the surrounding area

Problem: Given the question: What is the missing first step of the following process: - Embryo is C - Embryo grows and develops into a fetus inside the woman's womb - The fetus is born - Begins to grow and develop through infancy and childhood - In the teenage years the human experiences puberty - Reaches sexual maturity - At 18 the human becomes an adult - Adult may procreate continuing the cycle.
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The answer is:
A man and woman mate

Problem: Given the question: What is the missing first step of the following process: - The receptors will lock onto a target cell using these chemical receptors on the surface, which docks onto the cell surface - The receptors then go into the cell - The receptors use it like a factory - The receptors take it over and make it produce thousands or in some cases millions of copies of new viruses - The copies come streaming out of the cell - The copies infect other cells to make more viruses, or they escape from the body and infect a new victim -
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The answer is:
The flu virus has receptors, which are like viral Velcro, on the surface of the virus particle