Darby finds a rock in her backyard. it has large crystals. she has found

-an extrusive igneous rock
-an intrusive igneous rock
-basalt
-obsidian

Darby has found  an extrusive igneous rock   in her backyard.

... Lucky her.

where is the scientific experiment?

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.