The reason for the length of day and night is the diurnal rotation because the sun cannot illuminate the whole earth at once when the earth is lit on one side it is day and when it is on the other side it is night

Yes.

Explanation:

Yes, the sun cannot illuminate the whole earth at once when the earth is lit on one side it is day and when it is on the other side it is night. The earth rotates on its own axis which causes change of day and night. Due to this rotation, those areas which are in front of sun experience day while on the other hand, the shade part of the earth causes night at that part so we can say that  diurnal rotation is responsible for day and night.

b.have there own function.

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.