Within each intervertebral foramen, an ventral root and a dorsal root unite to form a

answer; i believe that the correct answer is(d) nondisjunction during meiosis;

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.