[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: - The sediment rolls down hill towards a river - The heavy items sink to the bottom - The lighter items float on the top and in convection cycles - As the river flows the sediment is moved - The sediment gets dumped through tributaries into lakes and the ocean - The sediment keeps moving around the world in convection currents.
****
[A]: Sediment becomes loose from the rest of the soil

[Q]: What is the missing first step of the following process: - As the plates move, they exert a great force - When the force is large enough, the crust breaks - The stress is released as energy - The energy moves through the Earth in the form of waves - We feel the earthquake -
****
[A]: Plates on the Earth's crust move slowly past each other

[Q]: What is the missing first step of the following process: - They secrete digestive juice 'externally' into the small intestine - There are enzymes for breaking down fats, proteins , and carbohydrates - Digestive juices flows from the pancreas through an excretory duct into the small intestine - When the blood sugar levels rise, as they might after a meal, insulin is released - When blood sugar levels are too low, the pancreas releases glucagon into the bloodstream -
****
[A]:
Over 99% of the exocrine pancreas cells produce digestive juices