Gases, like oxygen and carbon dioxide, move across cell membranes using simple diffusion. When ions can pass through the membrane without the aid of other molecules, and since oxygen and carbon dioxide can pass through the membrane, it is known as simple diffusion.
Answer:
Defenitely b, fossils, I don't think any of the others are right, But I could be wrong.
The ancient Egyptians used the stars to tell when a flood was going to happen. Every summer a flood would happen but this also happened when the bright star Sirius rose before the sun.
Hope that helped ^^
