The dense needles of Douglas fir trees can prevent most light from reaching the forest
floor. This situation would have an immediate
effect on ?

the answer is

c. parental

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.