If a piece of pure iron is placed in pure nitrogen, nothing happens. If the iron is exposed to air, it begins to rust. What conclusion can you make about air, based on this observation?

Read the following summary, which describes a body process. Then, answer the question. Blood enters the right side of the heart and travels to the lungs. There, the lungs eliminate carbon dioxide and exchange it for more oxygen.

Plant cells and animal cells possess many of the same organelles. Which of the following organelles, however, would be indicative of a plant cell rather than an animal cell? A. ribosome B. nucleus C. mitochondrion D. chloroplast

Explain how the earth surface can change as a result of global warming?

Explain why a person with thrombocytopenia purpurea shows many bruises or purple marks?

Which types of organisms are most likely to survive change in an ecosystem, those that have a narrow ecological niche or those that have a broad niche?

When an ocean wave reaches shallow water the energy of the wave ... A. pushes water up B. Returns water to the ocean C. Becomes stronger D. Disappears

By what process do all living organisms grow and repair themselves?

What is the name of the heart's contraction?

Which describes the habitat of a frog?

The size of a population refers to the