65 million years ago there was a mass extinction that is best known for killing the dinosaurs. There was also a large deposit of dust that contained substances only found in asteroids. What most likely killed off the dinosaurs? An asteroid impact caused the Sun to be blocked. They were crushed by an asteroid. The water supplies were polluted. Mammals evolved to be better competitors.

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.

if you look up in the top right corner you'll see your current profile picture, click than click "view profile" you'll be able to change it there.