Across 2. One of two places where air enters your body.
4. When we exhale we breathe this plus carbon dioxide.
7. You do this when something irritates your nose.
8. You do this when you don't get enough oxygen to your blood.
11. A gas that you breathe out. It is a waste gas.
14. The place where oxygen enters the blood.
16. You do this when something irritates your diaphragm.
17. Breathe out.
19. Large muscle that controls the lungs.
Down
1. This prevents food from going down your lungs.
3. All animals need this gas to make energy from food.
5. Scientific name for the windpipe.
6. Inhale and exhale.
9. Common name for the trachea.
10. Fish have these instead of lungs.
11. You do this when something irritates your trachea or bronchi.
12. Two tubes that connect the trachea to the lungs.
13. Breathe in.
15. One of two places where air enters your body.
18. What we breathe.

answer attached

Explanation:

hope this helps!

d concave shape of wave rock

explanation:

the concave shape of wave rock is a very good evidence that supports the evolution of earth due to chemical weathering. if we talk about structure of   wave rock, studies have estimated that it is around 2.7 billion years old. it also serves as the foundation of evidence that it was the place where australian continent began to form.

how the structure of wave rock was created?

studies suggest that structure of wave rock was created when the surrounded area was started to weather due to which deposition of material started on the part of land which now contains wave rock.

the structure of wave rock is considered to be one of the best-known landforms in australia. at the height of around 15 cm, there can be found flared slopes which formulate the margins of hyden rock. it is now assumed by geologists that wave rock was created by subsurface water-induced weathering and not by glaciers, waves or wind.

due to deposition of material over the period of long time, the wave rock became tougher and tougher due to weathering from surrounding terrain. this makes it a physical evidence that supports   the evolution of earth due to chemical weathering.

hope it !

the answer to your question is:

c. complementary base-pairing