Explain why the chemical composition of water is always the same? I forgot my textbook at school and can’t find the answer anywhere

How do dying stars contribute to the formation of planets

How many moles of no2 will form when 3.3 moles of cu are reacted with excess hno3?

Which of these statements best explains why space exploration should be encouraged? it prepares humans to live without oxygen. it dispel myths about objects in space. it prevents comets and asteroids from striking earth. it creates technology to absorb harmful radiations in space.