Problem: - Composition of blood is regulated - Volume of water in blood is kept constant - PH is kept at a constant level - Kidneys help regulate blood pressure - Kidneys stimulate the making of red blood cells - Calcium levels are maintained. What might be the first step of the process?

A: Kidneys filter waste out of blood

Problem: - The gases come to a head and push molten magma to the surface - The magma cools - With enough time the pressure builds up greatly - The resulting volcano may explode. What might be the first step of the process?

A: Gases cause pressure beneath the earth

Problem: - The gases come to a head and push molten magma to the surface - The magma cools - With enough time the pressure builds up greatly - The resulting volcano may explode. What might be the first step of the process?

A: Gases cause pressure beneath the earth

Problem: - The person's blood sugar level rises - The pancreas receives a signal to release insulin - Insulin is released into the bloodstream - Insulin signals cells to absorb sugar - The cells absorb sugar from the bloodstream - The cells use the sugar as energy. What might be the first step of the process?

A:
A person eats food