We ... oxygen.
breathe in
What do we breathe out?
We breathe out carbon dioxide.
We ... carbon dioxide.
breathe out
Our lungs get smaller when we ...
breathe out
Our lungs ... when we breathe in.
get bigger
What do we breathe in?
We breathe in oxygen.
Our lungs ... when we breathe out.
get smaller
Our lungs get bigger when we ...
breathe in