Q: 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

Q: What is the missing first step of the following process: - Water is transported to the leaves in the xylem - Energy harvested through light reaction is stored by forming ATP - Carbon dioxide and energy from ATP are used to create sugar - Oxygen exits the leaves through the stomata by diffusion - The plant reuses the water or the water exits through the stomata as water vapor.
A: Carbon dioxide enters the leaves through the stomates by diffusion

Q: What is the missing first step of the following process: - Cells in the pancreas release insulin - Insulin causes the body to absorb glucose from the blood - Blood sugar goes back to normal - Blood sugar is too low - The amount of insulin goes down - Cells in the pancreas release glucagon - The liver turns stored glycogen into glucose - The liver releases the glucose into the blood - Blood sugar goes back to normal.
A: Blood sugar levels increase after a meal

Q: 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.
A:
An area is at a higher elevation than the surrounding area