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