Problem: What is the missing first step of the following process:  -  The oxygen travels into the lungs - The oxygen binds to hemoglobin proteins within erythrocytes (red blood cells) - The erythrocytes are pumped through the body by the heart - All cells receive the oxygen.

A: Oxygen enters the body through the mouth or nose


Problem: What is the missing first step of the following process:  -  Coal is pulverized into fine powder - The coal is mixed with hot air - The coal and hot air are blown into a boiler - The coal and hot air burn over a fire - Highly purified water is pumped through pipes in the boiler - The water turns into steam - The steam presses against turbines - The turbines spin - Electricity is produced.

A: Coal is mined out of the ground


Problem: What is the missing first step of the following process:  -  Your stomach digests the food - Sugars from food enter your bloodstream - Insulin helps turn sugars into energy - Insulin helps your body store the energy in fat, muscle and liver cells -

A: You eat food


Problem: What is the missing first step of the following process:  -  The trees die off - The dead material provides nutrients for more trees - The rising trees provide shelter - And more organisms begin to thrive - The ecosystem known as a forest is made.

A:
Networks of trees start forming