Answer:
A gas-powered lawn mower is a complex machine because for it to function it does more than one motion. For example, it has a wheel and axle system so it can move when powered. And it has a system of simple machines and other parts that are put together to accomplish the task of cutting grass.
Explanation:
Genetics, Medical problems, eating habits etc
Answer:
Ozone layer... pollution
Explanation:
The ozone layer is a layer in the atmosphere which provides a barrier between harmful UV rays and the Earth. However, pollution is quickly depleting the layer which in turn creates a higher risk of skin cancers and other conditions caused by harmful UV rays.