1.  Fill in the gaps in the following sentences:         In the upper atmosphere, the name of the gas in the layer that reduces the amount of ultraviolet         radiation reaching the Earth's surface is          .            Exposure to ultraviolet radiation can cause           ,           and                      .         Environmental pollution from              is depleting the ozone layer.         The higher the risk factor of a sun block the              the skin can be exposed without burning.    2.  Hannah can stay in the Sun for 30 minutes without burning.          What is the longest time she can safely stay in the Sun  if she uses a sunscreen with a sun         protection factor number 15?    3.  How Science Works         Choose the correct answer:         Scientists say that high factor sun block can reduce damage from ultraviolet, this is based on ...         a prediction / a theory / data / a hypothesis.