Problem: What is the missing first step of the following process: - Falls onto the ground - The acid rain starts scouring rocks - Destroys vegetation - The lack of vegetation alters the surrounding environment.

A: Acid rain is produced by chemicals that reach into the atmosphere

Problem: What is the missing first step of the following process: - Babies become infants - Infants become children - Children learn skills - Children become teenagers - Teenagers undergo puberty - Teenagers become adults - Adults have children - Adults become elderly - Elderly humans die.

A: Humans are born as babies

Problem: What is the missing first step of the following process: - The boiler produces steam under high pressure - The steam generated in the boiler flows down into a cylinder - Just ahead of the wheels, pushing a tight-fitting plunger, the piston - The piston is connected to one or more of the locomotive's wheels through a kind of arm-elbow-shoulder joint called a crank and connecting rod - As the piston pushes, the crank and connecting rod turn the locomotive's wheels and power the train along - An outlet valve opens and the piston pushes the steam back through the cylinder and out up the locomotive's chimney -

A: Coal is loaded into the firebox

Problem: What is the missing first step of the following process: - The plant roots begin to grow - Break apart the rock - The plant acids dissolve parts of the rock - The rocks are broken into more and more pieces - Erosion starts to occur.

A:
A plant grows near or on a rock