Q: What is the missing first step of the following process:  -  The pollution negatively affects the water quality - The pollution negatively affects the health of plants and animals - The plants and animals have shorter, less healthy lives - The plants and animals do not reproduce very well - The number of plants and animals decreases over time - The quality of water gets worse and worse as there are no plants or animals to clean it - Eventually there is nothing living in the water and it is unusable -
A: Pollution enters natural water sources such as rivers and lakes

Q: What is the missing first step of the following process:  -  May come from different sources - The gases remain trapped in the atmosphere - Through the suns light the gases hold in heat and energy - Trap them in our atmosphere - The earth may become warmer this way.
A: Several types of gases form in the atmosphere

Q: What is the missing first step of the following process:  -  A large amount of rain occurs - The water builds up behind the dam - The dam opens its floodgates when it starts to get full - The water flows into a river below the dam - The dam closes its gates - The dam will occasionally open its gates again to gradually release more water - Eventually all of the floodwater will be slowly released into the river without causing any flood damage.
A: A dam is built in an area prone to flooding

Q: What is the missing first step of the following process:  -  They are born and are a baby - The baby grows into a child - Puberty turns the child into an adolescent - The adolescent becomes an adult - An adult becomes an elderly person - The elderly person dies.
A: