Half of the moon is always illuminated by the sun. given that this is true, then what causes the moon to change phases throughout the month? give a detailed explanation, .

It is true that only half of the moon is always illuminated by the sun.  The reason why the moon changes it phases is because Moon orbits around the Earth, and due to this some areas of the half of the moon will not be lit by the sun.

carla slowed down in the beginning of her trip, stopped, and then sped up