Problem: What is the missing first step of the following process: - Once in the lungs, oxygen is moved into the bloodstream and carried through your body - At each cell in your body, oxygen is exchanged for a waste gas called carbon dioxide - Your bloodstream then carries this waste gas back to the lungs where it is removed from the blood stream and then exhaled - Your lungs and respiratory system automatically perform this vital process, called gas exchange -

A: He air we breathe contains oxygen and other gases

Problem: What is the missing first step of the following process: - The plants and floor absorb the the sunlight - The absorbed sunlight is converted to heat - The heat cannot escape the glass - The heat is trapped in the greenhouse - The hot air rises - The colder air at the top is pushed to the bottom - The colder air is then warmed by the floor and the plants.

A: Sunlight passes through the glass into the greenhouse

Problem: What is the missing first step of the following process: - The magma goes into volcanos - The volcanos pressure the magma upwards - The pressure causes the magma to push through the surface of the volcano - The lava cools - The lava forms new rock - New magma is pressured to the surface of the volcano - The volcano bursts through the rock the formed after the last eruption.

A: Magma rises from deep in the earth

Problem: What is the missing first step of the following process: - The atoms become unstable - The atoms split - In alpha decay, two protons and two neutrons are released from the atom - In beta decay, a neutron changes into a proton and an electron - The proton joins the nucleus of the atom - The electron is released -

A:
The nuclei of some atoms have too few or too many neutrons